Microchip

ABSTRACT

A microchip including a fluid circuit formed by a groove of a first substrate and a surface of a second substrate is provided. The fluid circuit includes a fluid retaining reservoir for containing a fluid. The fluid retaining reservoir includes a fluid outlet or outflow channel for allowing the fluid to flow out, and a partition dividing the fluid retaining reservoir into a first region including a fluid inlet for injecting a fluid into the fluid retaining reservoir and a second region including the fluid outlet or outflow channel. The partition includes at least one communication gate for allowing communication between the first region and the second region.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a microchip useful as a μ-TAS (MicroTotal Analysis System) or the like that is suitably used for suchpurposes as biochemical tests for DNA, protein, cell, immunity, andblood for example, chemical synthesis and environmental analysis. Morespecifically, the present invention relates to a microchip havingtherein a fluid retaining reservoir for containing a fluid such asreagent to be mixed or reacted with a sample to be tested or analyzedfor example.

2. Description of the Background Art

In recent years, in the fields of medical care, health, food, and drugdiscovery for example, sensing, detection or quantitation of biologicalsubstances such as DNA (Deoxyribo Nucleic Acid), enzyme, antigen,antibody, protein, virus, and cell as well as chemical substances hasbecome increasingly important, and various biochips and micro chemicalchips (they are hereinafter referred to collectively as microchip) withwhich the above-described substances can be easily and convenientlymeasured have been proposed. The microchip can be used to allow a seriesof experimental and analytical operations usually performed in alaboratory to be conducted within the chip of several centimeters perside and approximately several millimeters to one centimeter inthickness. The microchip accordingly provides many advantages that theamounts of samples and reagents to be used are very small, the cost islow, the reaction rate is high, high throughput test can be conducted,and the test results can be immediately obtained at the site where thesample was taken, for example. The microchip is suitably used forbiochemical tests such as blood test for example.

The microchip commonly includes therein “fluid circuit” that is a fluidchannel network constituted of portions (chambers) where a specifictreatment is performed on a fluid, and a fine fluid channelappropriately connecting these portions. In the test and analysis of asample (such as blood or a specific component of the blood for examplein the case of the blood test) by means of a microchip having thereinsuch a fluid circuit as described above, the fluid circuit is used toperform various fluid treatments such as measurement of a sampleintroduced into the fluid circuit, measurement of a reagent to be mixedwith the sample, and mixing of the sample with the reagent. The variousfluid treatments can be performed by applying a centrifugal force in anappropriate direction to the microchip.

A microchip having a fluid circuit in which a reagent to be mixed orreacted with a sample or a specific component in the sample is containedand retained in advance, namely so-called reagent-contained microchip,has been known (see for example Japanese Patent Laying-Open No.2007-017342, U.S. Pat. No. 4,883,763 and Japanese Patent Laying-Open No.2007-229631). The reagent-contained microchip usually includes, as apart of the fluid circuit of the microchip, one or a plurality ofreagent retaining reservoirs for retaining a reagent. Further, thereagent-contained microchip usually has a reagent inlet formed in one ofthe surfaces of the microchip and extending through to the reagentretaining reservoir for injecting a reagent into the reagent retainingreservoir. The reagent-contained microchip is produced in the followingmanner. A reagent is injected through the reagent inlet, and thereaftera sealing label (seal) or the like for example is bonded to the surfaceof the microchip to seal the reagent inlet. The microchip is shipped inthis state for use.

Regarding such a reagent-contained microchip, in order to perform a testand analysis for a sample with high precision, degradation of thecontained reagent has to be sufficiently suppressed or prevented fromthe time when the microchip is produced (when the reagent is injected)to the time when the microchip is actually used. Further, the reagentshould be sufficiently suppressed or prevented from flowing out of thereagent retaining reservoir, which could be caused for example by impacton the microchip or by an increase of the internal pressure of thereagent retaining reservoir during transportation and delivery of themicrochip for example. This is for the following reason. If the reagentdeteriorates or flows out of the reagent retaining reservoir, thereagent and the sample (or a specific component contained in the sample)will not properly react, or the microchip contains no reagent to bemixed with the sample (or a specific component contained in the sample)when the sample is tested and analyzed, or the reagent and the sample(or a specific component contained in the sample) are not mixed at anappropriate ratio, which could result in the possibility that accurateand highly reliable test and analysis results cannot be obtained.

U.S. Pat. No. 4,883,763 and Japanese Patent Laying-Open No. 2007-139480for example each disclose a reagent-contained microchip in which areagent contained in the microchip is sealed so that deterioration ofthe reagent and unintended outflow of the reagent can be prevented untilthe microchip is used. FIG. 21 is a plan view showing an example of thereagent-contained microchip disclosed in U.S. Pat. No. 4,883,763. In themicrochip shown in FIG. 21, chambers 96 and 98 retaining a reagent aresealed containers slidable with respect to a substrate and each havingan openable portion 10 where an opening can be made. At respectivepositions opposite to chambers 96 and 98, spike or needle-shaped openingmeans 12 are provided. This structure allows the reagent to be sealed inchambers 96 and 98 until the microchip is used. When the microchip isused, this structure allows the reagent to flow out through an openingmade in openable portion 10 by opening means 12 as a result ofapplication of a centrifugal force in F₀ direction shown in FIG. 21.

Although the above-described structure is highly effective at preventingdeterioration of the reagent and unintended outflow of the reagent,there is a possibility that the whole amount of the reagent does notflow out from the hole made by opening means 12. If some of the reagentremains in chamber 96 or 98, application of a centrifugal force in asubsequent fluid treatment process could cause the remaining reagent toflow out again to adversely affect mixing or reaction of the reagentwith a sample or adversely affect the results of the test and analysisof a fluid mixture of a sample and the reagent.

Further, the microchip disclosed in U.S. Pat. No. 4,883,763 has aproblem that the structure of the reagent retaining reservoir (chamber)is very complicated and thus the reservoir is not easy to produce.Specifically, it is necessary to provide a window in the container inwhich the reagent is sealed and further attach a film or the like to thewindow so that a hole can be formed with a needle or the like, asopenable portion 10. It is also necessary to slidably dispose thecontainer on the substrate. Further, since the microchip has a movableportion (slidable container), the microchip lacks operational stability.For example, when an operational failure of the movable portion occurs,the reagent may not flow out.

Japanese Patent Laying-Open No. 2007-229631 discloses a microreactor inwhich a liquid such as reagent or sample can be surely stopped at adesired position and the liquid can be surely restarted from theposition where the liquid is stopped. The disclosed microreactorincludes a water repellant valve constituted of an upstream sideconnection hole having a smaller cross-sectional area than thecross-sectional area of an upstream side flow channel, a downstream sideconnection hole having a smaller cross sectional area than thecross-sectional area of a downstream side flow channel, and a connectionhole communicating portion allowing communication between the upstreamside connection hole and the downstream side connection hole and havinga continuously varying cross-sectional area. On the two opposing ends ofa storage portion where a reagent or sample is stored, the waterrepellant valves are provided respectively (see in particular FIGS. 3and 5 of Japanese Patent Laying-Open No. 2007-229631).

Even if the water repellant valve having the above-described structureis provided, impact or an increase of the internal pressure for exampleduring transportation and delivery of the microchip could cause theliquid to move from a predetermined position or flow out. Thus, therestill has been room for improvement of the ability to retain a fluidsuch as reagent (ability to prevent outflow or leakage of the fluid).

SUMMARY OF THE INVENTION

The present invention has been made to solve the above-describedproblems, and an object of the invention is to provide a microchipincluding therein a fluid retaining reservoir having a relativelysimplified structure for containing a fluid such as reagent. In themicrochip having therein the fluid retaining reservoir, the reagent canbe retained in a nearly sealed state and, even if an external impact isapplied to the microchip or an internal pressure of the fluid retainingreservoir increases, for example, the reagent can be effectivelyprevented from outflowing from the fluid retaining reservoir.

Specifically, the present invention is a microchip including: a firstsubstrate and a second substrate, the first substrate being superposedon the second substrate and having a surface with a groove; and a fluidcircuit composed of a cavity defined by the groove of the firstsubstrate and a surface on the first substrate side of the secondsubstrate. The fluid circuit includes a fluid retaining reservoir forcontaining a fluid. The first substrate has a fluid inlet for injectinga fluid into the fluid retaining reservoir, and the fluid inlet is athrough opening extending through the first substrate from a surfaceopposite to the surface with the groove of the first substrate to thefluid retaining reservoir. The fluid retaining reservoir includes: afluid outlet or outflow channel for allowing the fluid to flow out; anda partition dividing the fluid retaining reservoir into a first regionincluding the fluid inlet and a second region including the fluid outletor outflow channel. The partition includes at least one communicationgate for allowing communication between the first region and the secondregion.

Preferably, the partition includes two communication gates. In thiscase, preferably the two communication gates are disposed respectivelyat two opposing ends of the partition.

Preferably, a cross section, parallel to the surface with the groove ofthe first substrate, of at least a part of the partition has asubstantially V shape or substantially U shape protruding toward thefirst region. Alternatively, preferably a cross section, parallel to thesurface with the groove of the first substrate, of at least a part ofthe partition has a substantially V shape or substantially U shapeprotruding toward the second region.

The height of the communication gate at an end abutting on the firstregion and the height of the communication gate at an end abutting onthe second region may be substantially equal to each other.Alternatively, the communication gate may have an upper inner wallinclining in such a manner that the height of the communication gatedecreases from the first region toward the second region. “Upper” hereinrefers to the upper side when the first substrate is superposed on thesecond substrate.

Further, in the first region, a region adjacent to the communicationgate may have an upper inner wall inclining in such a manner that, inthe region adjacent to the communication gate, the height of the fluidretaining reservoir decreases toward the communication gate.

The microchip of the present invention having the above-describedstructure may be a liquid-reagent-contained microchip in which a liquidreagent is contained in a liquid reagent retaining portion that is afluid retaining reservoir of the microchip. In this case, a liquidreagent inlet serving as a fluid inlet is sealed on the surface of themicrochip on the side having the inlet (namely the surface of the firstsubstrate) by attaching for example a sealing label or sealing seal.

The present invention is also a microchip including: a first substrateand a second substrate, the first substrate being superposed on thesecond substrate and having a surface with a groove; and a fluid circuitcomposed of a cavity defined by the groove of the first substrate and asurface on the first substrate side of the second substrate. The fluidcircuit includes a fluid retaining reservoir that is a portion forretaining a fluid and includes a first outlet or first outflow channelfor allowing the fluid to flow out; and a fluid containing reservoirthat is a portion connected to the first outlet or first outflow channelfor containing the fluid flowing out from the fluid retaining reservoirand includes a second outlet or second outflow channel for allowing thefluid to flow out.

In a preferred embodiment, the fluid retaining reservoir includes afirst outflow channel for allowing the fluid to flow out, and the fluidcontaining reservoir includes a second outflow channel for allowing thefluid to flow out. In this case, preferably the second outflow channelextends in a direction different from the direction in which the firstoutflow channel extends.

In the case where the fluid containing reservoir includes a secondoutflow channel for allowing the fluid to flow out, preferably an end ofthe second outflow channel is connected to a measurement portion formeasuring the fluid.

Preferably, the first substrate includes a fluid inlet for injecting afluid into the fluid retaining reservoir. The fluid inlet is a throughopening extending through the first substrate from a surface opposite tothe surface with the groove of the first substrate to the fluidretaining reservoir. In this case, preferably the fluid retainingreservoir includes a partition dividing the fluid retaining reservoirinto a first region having the fluid inlet and a second region having afirst outlet or first outflow channel, and the partition includes atleast one communication gate for allowing communication between thefirst region and the second region.

Preferably, the partition includes two communication gates. In thiscase, preferably the two communication gates are disposed respectivelyat two opposing ends of the partition.

Preferably, a cross section, parallel to the surface with the groove ofthe first substrate, of at least a part of the partition has asubstantially V shape or substantially U shape protruding toward thefirst region. Alternatively, preferably a cross section, parallel to thesurface with the groove of the first substrate, of at least a part ofthe partition has a substantially V shape or substantially U shapeprotruding toward the second region.

The height of the communication gate at an end abutting on the firstregion and the height of the communication gate at an end abutting onthe second region may be substantially equal to each other.Alternatively, the communication gate may have an upper inner wallinclining in such a manner that the height of the communication gatedecreases from the first region toward the second region. “Upper” hereinrefers to the upper side when the first substrate is superposed on thesecond substrate.

Further, in the first region, a region adjacent to the communicationgate may have an upper inner wall inclining in such a manner that, inthe region adjacent to the communication gate, the height of the fluidretaining reservoir decreases toward the communication gate.

The microchip of the present invention having the above-describedstructure may be a liquid-reagent-contained microchip in which a liquidreagent is retained in a liquid reagent retaining portion that is afluid retaining reservoir of the microchip. In this case, a liquidreagent inlet serving as a fluid inlet is sealed on the surface of themicrochip on the side having the inlet (namely the surface of the firstsubstrate) by attaching for example a sealing label or sealing seal.

The present invention is also a microchip including: a first substrateand a second substrate, the first substrate being superposed on thesecond substrate and having a surface with a groove; and a fluid circuitcomposed of a cavity defined by the groove and a surface on the firstsubstrate side of the second substrate. The fluid circuit includes afluid retaining reservoir for retaining a fluid. The fluid retainingreservoir includes: a fluid outlet for allowing the fluid to flow outfrom the fluid retaining reservoir; and a partition dividing the fluidretaining reservoir into a first region where the fluid is introducedand a second region where the fluid outlet is included. The partitionincludes a communication gate for allowing communication between thefirst region and the second region. At least a part of the partitionincludes a curved portion formed of a wall in a shape of a curve as seenfrom a surface of the microchip.

Preferably the curved portion is formed of a wall in a shape of an arcprotruding toward the second region. Preferably the arc has a radius ofcurvature of 2 to 5 mm.

Further, preferably a side surface of the partition abutting on thefirst region has an inclined surface inclined with respect to thicknessdirection of the microchip.

In a preferred embodiment, the partition is composed of a protrusionprovided on a surface of the first substrate or the second substrate,and the communication gate is composed of a space defined between theprotrusion and an opposite surface of the second substrate or the firstsubstrate. In this case, preferably a surface of the protrusion formingthe communication gate extends parallel or substantially parallel to theopposite surface of the second substrate or the first substrate.Further, preferably an angle between the surface of the first substrateor the second substrate having the protrusion provided thereon andforming the first region, and a side surface of the protrusion abuttingon the first region, is an obtuse angle.

In another preferred embodiment, the partition is composed of respectiveprotrusions provided on respective surfaces of the first substrate andthe second substrate, and the communication gate is composed of a spacedefined between the protrusion provided on the surface of the firstsubstrate and a protrusion provided on the surface of the secondsubstrate. In this case, preferably the protrusion provided on thesurface of the first substrate and the protrusion provided on thesurface of the second substrate have respective surfaces forming thecommunication gate that are parallel to or substantially parallel toeach other. Further, preferably an angle between the surface of thefirst substrate forming the first region, and a side surface, abuttingon the first region, of the protrusion provided on the surface of thefirst substrate, is an obtuse angle, and an angle between the surface ofthe second substrate forming the first region, and a side surface,abutting on the first region, of the protrusion provided on the surfaceof the second substrate, is an obtuse angle.

Furthermore, the present invention is a microchip including: a firstsubstrate and a second substrate, the first substrate being superposedon the second substrate and having a surface with a groove; and a fluidcircuit composed of a cavity defined by the groove and a surface on thefirst substrate side of the second substrate. The fluid circuit includesa fluid retaining reservoir for containing a fluid. The fluid retainingreservoir includes: a fluid outlet for allowing the fluid to flow out;and at least one columnar body extending in thickness direction of themicrochip. The columnar body is provided in a fluid retaining region forretaining the fluid. The fluid retaining region includes a positionfarthest from the fluid outlet.

Preferably the fluid retaining reservoir includes at least threecolumnar bodies, and the columnar bodies are disposed at respectivepositions corresponding to vertexes of a substantially regular triangle.In this case, preferably the columnar bodies are disposed in such amanner that one side of the substantially regular triangle is 0.5 to 1mm.

Further, preferably the fluid retaining reservoir includes at least twocolumnar bodies, and the columnar bodies are arranged on a surface ofthe fluid formed when the whole amount of the fluid contained in thefluid retaining reservoir is retained in the fluid retaining region.

Preferably, the length of the columnar body in the thickness directionof the microchip is substantially identical to the depth of the grooveforming the fluid retaining reservoir.

Preferably, the first substrate includes a fluid inlet for injecting thefluid into the fluid retaining reservoir, the fluid inlet is a throughopening extending through the first substrate from a surface opposite tothe surface with the groove of the first substrate to the fluidretaining reservoir, and at least two columnar bodies are arrangedsubstantially perpendicularly to a line connecting the fluid outlet andthe center of the fluid inlet.

Further, the present invention provides a substrate that is theabove-described first substrate where the columnar body is disposed inthe groove forming the fluid retaining reservoir, and a substrate thatis the above-described second substrate where the columnar body isdisposed in the groove forming the fluid retaining reservoir.

According to the microchip of the present invention, even if an externalimpact is applied or the internal pressure of the fluid retainingreservoir increases due to variation of the environmental temperaturefor example, the fluid (such as liquid reagent) contained in thereservoir can be effectively prevented from flowing out from the fluidretaining reservoir. Further, since the fluid retaining reservoir in themicrochip of the present invention can retain the fluid in a staterelatively close to a sealed state, an excellent ability to preventdegradation of the fluid is achieved. Furthermore, since the fluidretaining reservoir has a relatively simplified structure, the reservoiris easy to manufacture and problems such as operational malfunction areunlikely to occur.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a preferred example of a first substratehaving a groove in a surface, and used for a microchip according to afirst embodiment of the present invention.

FIG. 2 is an enlarged plan view of a liquid reagent retaining portion ofthe first substrate shown in FIG. 1.

FIG. 3 is a schematic cross-sectional view of a partition along lineI-I′ shown in FIG. 2.

FIG. 4 is a schematic diagram showing an example of a cross section ofthe partition along line II-II′ shown in FIG. 2.

FIG. 5 is an enlarged plan view showing another preferred example of theliquid reagent retaining portion according to the first embodiment ofthe present invention.

FIG. 6 is a schematic cross-sectional view of a partition and itsperipheral portion along line III-III′ shown in FIG. 5.

FIG. 7 is a top view showing a preferred example of a microchipaccording to a second embodiment of the present invention, formed bysuperposing and bonding a first substrate having a groove in a surfaceonto a second substrate.

FIG. 8 is an enlarged top view of a liquid reagent retaining portion andits peripheral portion of the microchip shown in FIG. 7.

FIG. 9 is an enlarged top view of a liquid reagent retaining portion andits peripheral portion in another preferred example of the microchipaccording to the second embodiment of the present invention.

FIG. 10 is a top view showing a preferred example of a microchipaccording to a third embodiment of the present invention, formed bysuperposing and bonding a first substrate having a groove formed in asurface onto a second substrate.

FIG. 11 is an enlarged top view of a liquid reagent retaining portion ofthe microchip shown in FIG. 10.

FIG. 12 is a schematic cross-sectional view along line XII-XII shown inFIG. 11.

FIG. 13 is a schematic cross-sectional view showing another example ofthe liquid reagent retaining portion of the microchip according to thethird embodiment of the present invention.

FIG. 14 is a schematic cross-sectional view showing still anotherexample of the liquid reagent retaining portion of the microchipaccording to the third embodiment of the present invention.

FIG. 15 is a plan view showing a preferred example of a first substratehaving a groove formed in a surface and used for a microchip accordingto a fourth embodiment of the present invention.

FIG. 16 is an enlarged plan view of a liquid reagent retaining portionof the first substrate shown in FIG. 15.

FIG. 17 is an enlarged diagram showing an arrangement of columnar bodiesin the liquid reagent retaining portion shown in FIG. 16.

FIG. 18 is a plan view showing a relation between a plurality ofcolumnar bodies in the liquid reagent retaining portion shown in FIG. 16and a liquid reagent retained in the liquid reagent retaining portion.

FIG. 19 is a cross-sectional view along line XIX-XIX shown in FIG. 16.

FIG. 20 is a plan view showing a microchip without columnar body.

FIG. 21 is a plan view showing an example of a conventionalreagent-contained microchip.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A microchip in the present embodiment is a chip with which various typesof chemical synthesis, test and analysis for example can be performed bymeans of a fluid circuit of the microchip. The microchip of the presentembodiment in a preferred form is constituted of a second substrate anda first substrate superposed on and bonded onto the second substrate.More specifically, the first substrate having a groove in its surface isbonded onto the second substrate in such a manner that the groove-formedsurface of the first substrate is opposite to the second substrate.Thus, the microchip formed of these two substrates includes therein afluid circuit composed of a cavity defined by the groove provided in thesurface of the first substrate and one of the surfaces of the secondsubstrate that is opposite to the first substrate. While the shape andpattern of the groove formed in the surface of the first substrate arenot particularly limited to specific ones, the shape and pattern of thegroove are determined so that the structure of the cavity made by thegroove and the surface of the second substrate is a desired appropriatefluid circuit structure. The first-substrate-side surface of the secondsubstrate may have a groove as well with which a fluid circuit can beformed.

The microchip of the present embodiment in another preferred form isconstituted of a first substrate having grooves respectively provided inopposite surfaces of the first substrate, and second and thirdsubstrates superposed and bonded in such a manner that the firstsubstrate is sandwiched between the second and third substrates.

The microchip constituted of these three substrates includes two layersof fluid circuits, namely a first fluid circuit composed of a cavitydefined by one of the surfaces of the second substrate that is oppositeto the first substrate and the groove formed in the surface of the firstsubstrate that is opposite to the second substrate, and a second fluidcircuit composed of a cavity defined by one of the surfaces of the thirdsubstrate that is opposite to the first substrate and the groove formedin the surface of the first substrate that is opposite to the thirdsubstrate. Here, “two layers” means that the fluid circuits are providedrespectively at two positions that are different in the thicknessdirection of the microchip. The first fluid circuit and the second fluidcircuit may be connected by one through opening or two or more throughopenings extending through the first substrate in the thicknessdirection. Further, in the first-substrate-side surfaces/surface of thesecond substrate and/or the third substrate as well, grooves/groove maybe formed with which a fluid circuit can be formed.

The method for bonding the substrates together is not particularlylimited to a specific one, and includes those methods such as a methodfor welding the substrates together by melting a to-be-bonded surface ofat least one of the substrates to be bonded to each other (weldingmethod), and a method for joining the substrates together by means of anadhesive, for example. The welding method includes those methods such asa method for welding the substrates together by heating the substrates,a method for welding the substrates together by means of heat generatedwhen the light such as a laser is absorbed, and a method for welding thesubstrates together by means of ultrasonic waves.

The size of the microchip in the present embodiment is not particularlylimited to a specific one, and may be approximately several centimetersin length and width each and approximately several millimeters to onecentimeter in thickness.

The material for each of the substrates constituting the microchip inthe present embodiment is not particularly limited to a specific one,and may be for example any of organic materials such as polyethyleneterephthalate (PET), polybutylene terephthalate (PBT),polymethylmethacrylate (PMMA), polycarbonate (PC), polystyrene (PS),polypropylene (PP), polyethylene (PE), polyethylene naphthalate (PEN),polyarylate resin (PAR), acrylonitrile-butadiene-styrene (ABS) resin,polyvinyl chloride (PVC) resin, polymethylpentene (PMP) resin,polybutadiene (PBD) resin, biodegradable polymer (BP), cycloolefinpolymer (COP), and polydimethylsiloxane (PDMS), and inorganic materialssuch as silicon, glass and quartz.

In the case where the microchip is constituted of two substrates: firstsubstrate and second substrate, the first substrate having a groove inits surface and superposed on the second substrate is not particularlylimited to a specific one, and may be for example a transparentsubstrate. Thus, as a part of the fluid circuit, a detecting portionmade by the groove of the transparent first substrate and the surface ofthe second substrate can be formed. In the microchip having such adetecting portion, a subject to be measured (such as a liquid mixture ofa sample to be tested and analyzed and a liquid reagent for example) isintroduced into the detecting portion, light is applied to the detectingportion and the intensity (transmittance) of the transmitted light isdetected. Thus, the microchip can be used to perform the opticalmeasurement as described above for such a liquid mixture. The secondsubstrate may be a transparent substrate or a colored substrate such asblack substrate made of a resin to which carbon black for example isadded. The second substrate is preferably a colored substrate, and morepreferably a black substrate. A colored substrate can be used as thesecond substrate so that the welding method by means of light such as alaser can be used. In the case where substrates are bonded togetherusing the laser welding method, the bonding surface of the coloredsubstrate is chiefly melt to be bonded. Therefore, deformation of thegroove formed in the transparent substrate that is the first substratecan be kept minimum.

In the case where the microchip is constituted of three substrates:first substrate, second substrate and third substrate, the secondsubstrate and the third substrate holding therebetween the firstsubstrate with respective grooves in the opposite surfaces are notparticularly limited to specific ones, and may be transparentsubstrates. Thus, as a part of the fluid circuit, a detecting portionformed by a through opening extending through the first substrate in thethickness direction of the substrate and respective surfaces of thetransparent second and third substrates can be formed. In the microchiphaving such a detecting portion, a subject to be measured (such as aliquid mixture of a sample to be tested and analyzed and a liquidreagent for example) is introduced into the detecting portion, light inthe direction perpendicular to the microchip surface is applied from theupper surface (or lower surface) side of the microchip to the detectingportion, and the intensity (transmittance) of the transmitted light isdetected on the opposite side to the light incident side. Thus, themicrochip can be used to perform the optical measurement as describedabove for such a liquid mixture. The first substrate located between thesecond substrate and the third substrate is preferably a coloredsubstrate and more preferably a black substrate.

The method for forming a groove (flow channel pattern) by which thefluid circuit is made not particularly limited to a specific one, andexamples of the method include injection molding method using a moldhaving a transfer structure and imprinting method for example. In thecase where an inorganic material is used to form the substrate, etchingmay be used for example.

In the microchip of the present embodiment, the fluid circuit (a firstfluid circuit and a second fluid circuit where fluid circuits of twolayers are included) includes various portions disposed at appropriatepositions in the fluid circuit so that various appropriate treatmentscan be performed on the fluid (such as liquid) in the fluid circuit, andthese portions are appropriately connected via a fine flow channel.

In the microchip of the present embodiment, the fluid circuit of themicrochip includes, as one of the components of the fluid circuit, aliquid reagent retaining portion serving as a fluid retaining reservoirthat is a portion for retaining a liquid reagent which is a fluid. Onlyone fluid retaining reservoir (such as liquid reagent retaining portion)or two or more fluid retaining reservoirs may be provided in the fluidcircuit. “Fluid” refers to a substance with fluidity such as liquid forexample. “Liquid reagent” refers to a liquid substance to be mixed orreacted with a sample to be tested and analyzed. One type of liquidreagent or two or more types of liquid reagents may be contained withinone microchip. “Sample” refers to a substance (such as blood) itselfintroduced into the fluid circuit for undergoing a test and an analysis,or a specific component (such as blood plasma component) in thesubstance.

In the case where the microchip of the present embodiment is constitutedof two substrates (first substrate and second substrate), the microchipof the present embodiment is provided with a liquid reagent inlet forinjecting a liquid reagent into the liquid reagent retaining portion.The liquid reagent inlet serves as a fluid inlet that is a throughopening formed in the upper side surface (namely the surface of thefirst substrate) and extending through to the inside liquid reagentretaining portion (extending through the first substrate in thedirection of the thickness of the first substrate). In such a microchip,usually a liquid reagent which is a fluid is injected from the liquidreagent inlet and thereafter a label or seal is adhered to the surfaceof the microchip (surface of the first substrate) for sealing the liquidreagent inlet, and accordingly the microchip is provided for use. In thecase where the microchip is constituted of three substrates (secondsubstrate/first substrate/third substrate), a liquid reagent inlet maybe provided as a through opening extending from the upper side surfaceof the microchip (the surface of the second or third substrate) to theinside liquid reagent retaining portion (extending through the second orthird substrate in the direction of the thickness thereof).

In the microchip of the present embodiment, the fluid circuit mayinclude any component other than the fluid retaining reservoir (liquidreagent retaining portion). Examples of such a component include aseparating portion for extracting a specific component from a sampleintroduced into the fluid circuit, a sample measuring portion formeasuring a sample (or a specific component in the sample, the same isapplied as well to the following description), a fluid measuring portion(liquid reagent measuring portion) for measuring a fluid such as liquidreagent, a mixing portion for mixing a sample with a fluid such asliquid reagent, and a detecting portion (such as cuvette for performingoptical measurement) for testing and analyzing the resultant liquidmixture (detecting or quantitating a specific component in the liquidmixture) for example. The microchip of the present embodiment mayinclude all the above-illustrated components or may not include or oneor more of these components. The microchip may include any componentother than the above-illustrated components. These components aredisposed at appropriate positions in the fluid circuit and connected viaa fine flow channel, so that a desired fluid treatment can be performed.

The liquid mixture finally obtained by mixing a sample with a fluid suchas liquid reagent is provided for taking an optical measurement, forexample, detecting the intensity (transmittance) of the light applied toand transmitted through the component (detecting portion for example)containing the liquid mixture, and the liquid mixture is accordinglytested and analyzed.

Various fluid treatments to be performed in the fluid circuit, such asextraction of a specific component (separation of an unnecessarycomponent) from a sample, measurement of a sample and/or a fluid,mixture of a sample with a fluid, and introduction of the resultantliquid mixture into the detecting portion, for example, can be carriedout by successively applying a centrifugal force in an appropriatedirection to the microchip. The centrifugal force can be applied to themicrochip mounted on an apparatus (centrifugal apparatus) capable ofapplying a centrifugal force. The centrifugal apparatus includes afreely rotatable rotor (rotating body) and a freely rotatable stageplaced on the rotor. The microchip is mounted on the stage and the stageis rotated to set the angle of the microchip with respect to the rotorto an arbitrary angle, so that the centrifugal force in an arbitrarydirection can be applied to the microchip.

FIG. 1 is a plan view showing a preferred example of a first substrate100 having a groove formed in a surface and used for the microchip ofthe present embodiment, and showing the groove-formed side of firstsubstrate 100. The microchip of the present embodiment is formed bybonding first substrate 100 onto a second substrate (not shown)identical or similar in outline form to first substrate 100, in such amanner that the groove-formed surface of first substrate 100 is locatedopposite to the second substrate. First substrate 100 and the secondsubstrate are respectively a plastic transparent substrate and a plasticblack substrate, for example.

Referring to FIG. 1, the microchip of the present embodiment is chieflyconstituted of a sample tube mount portion 101 for incorporating asample tube such as capillary containing the whole blood taken from asubject, a blood plasma separating portion 102 for removing blood cellsfor example from the whole blood drawn from the sample tube to obtain ablood plasma component, a sample measuring portion 103 for measuring theseparated blood plasma component, two liquid reagent retaining portions104, 105 serving as fluid retaining reservoirs for retaining a liquidreagent, two liquid reagent measuring portions 106, 107 for measuringthe liquid reagent, mixing portions 108, 109, 110, 111 for mixing theblood plasma component with the liquid reagent, and a detecting portion112 for performing a test and an analysis of the resultant liquidmixture. Two liquid reagent retaining portions 104, 105 have respectiveliquid reagent inlets 113, 114 for injecting the liquid reagent. Liquidreagent inlets 113, 114 are each a through opening extending throughfirst substrate 100 in the direction of the thickness of the firstsubstrate.

FIG. 2 is an enlarged plan view of liquid reagent retaining portion 104of first substrate 100 shown in FIG. 1. As shown in FIG. 2, liquidreagent retaining portion 104 includes an outflow channel 120 forallowing the liquid reagent contained in the retaining portion to flowout. The end opening of outflow channel 120 is located above liquidreagent measuring portion 106. Thus, as a centrifugal force in thedownward direction with respect to FIG. 2 (or a centrifugal force in thedirection which includes the downward direction with respect to FIG. 2)is applied, for example, the liquid reagent in liquid reagent retainingportion 104 is discharged from the end opening of outflow channel 120and introduced into liquid reagent measuring portion 106 so that thereagent is measured.

In liquid reagent retaining portion 104, a partition 130 is provided fordividing liquid reagent retaining portion 104 into two sections: a firstregion A including liquid reagent inlet 113 and a second region Bincluding outflow channel 120. Partition 130 includes two communicationgates 131 respectively located at the two opposing ends of partition 130for allowing communication between first region A and second region B.Partition 130 has a V-shaped cross section in the direction parallel tothe surface of first substrate 100 (the surface having the groove) shownin FIG. 2. A similar partition is provided in liquid reagent retainingportion 105 as well, which will not be described in detail (see FIG. 1).

When a liquid reagent is injected into liquid reagent retaining portion104 of the microchip in the present embodiment structured in theabove-described manner, the liquid reagent injected from liquid reagentinlet 113 to be contained in first region A is less likely to flow outinto second region B even if an impact is exerted on the microchip,since two communication gates 131 function as a valve. Namely, theliquid reagent retaining portion of the microchip in the presentembodiment has a superior function of retaining the liquid reagentagainst impact, and thus can effectively suppress or prevent unintendedoutflow of the liquid reagent from the liquid reagent retaining portiondue to impact. The function of the valve here refers to the functionthat undesired discharge of the liquid reagent is prevented whiledesired discharge can be done by application of a centrifugal force witha predetermined strength. In the present embodiment, outflow channel 120also has the valve function. Therefore, liquid reagent retaining portion104 has the two-stage valve function. Since outflow channel 120 has thevalve function, even if any impact causes the liquid reagent to flow outfrom communication gate 131 into second region B, the possibility thatthe liquid reagent flows out of liquid reagent retaining portion 104 canbe made extremely low.

Further, as partition 130 is disposed, the liquid reagent being injectedinto liquid reagent retaining portion 104 can be suppressed or preventedfrom closing the inside opening (opening relatively closer to firstregion A) of outflow channel 120. Further, the reagent can be preventedfrom moving to close the inside opening of outflow channel 120 due toimpact as described above. Therefore, outflow, from the liquid reagentretaining portion, of the liquid reagent closing the inside opening canbe suppressed or prevented that is caused by an increase of the internalpressure in the liquid reagent retaining portion due to an increase ofthe environmental temperature.

FIG. 3 is a schematic cross-sectional view of partition 130 along lineI-I′ shown in FIG. 2. As shown in FIG. 3, communication gate 131 mayhave a square or rectangular cross section. In order to allowcommunication gate 131 to have the valve function, width W1 and heightW2 of communication gate 131 are each preferably 0.1 to 0.4 mm, and morepreferably 0.2 to 0.3 mm. If two or more communication gates areprovided like the example shown in FIG. 2, respective cross-sectionalshapes of the communication gates may be identical to or different fromeach other. Further, the cross-sectional shape of the communication gatemay be identical or may vary along the whole dimension in the directionof length (direction of the length refers to the direction of thicknessW3 of partition 130 shown in FIG. 2). Specifically, in the former case(the cross-sectional shape of communication gate 131 is identical alongthe whole dimension in the direction of thickness W3), the crosssectional shape of communication gate 131 at the end abutting on firstregion A, the cross sectional shape thereof at the other end abutting onsecond region B and the cross-sectional shape thereof between these endsare all identical or substantially identical to each other. Thecommunication gate having the above-described shape is preferablebecause such a communication gate is relatively easy to process.

In the case where the cross-sectional shape of the communication gatevaries in the direction of length (thickness W3), (i) height W2 of thecommunication gate is constant while width W1 continuously decreases orincreases, or (ii) width W1 of the communication gate is constant whileheight W2 continuously decreases or increases, for example. A morespecific example of case (ii) above is shown in FIG. 4. FIG. 4 is aschematic diagram showing an example of the cross section of partition130 along line IT-II′ shown in FIG. 2. In this example as shown in FIG.4, on the groove-formed surface of first substrate 100, the bottom ofthe groove that constitutes a part of the inner wall of communicationgate 131 becomes gradually shallower from first region A toward secondregion B to form an inclined surface M. Inclined surface M is thesurface forming the upper inner wall of the communication gate whenfirst substrate 100 is superposed on the second substrate (namely it issupposed here that the first substrate is located on the “upper side”with respect to the second substrate). Therefore, in the microchip usingfirst substrate 100 having the structure shown in FIG. 4, the upperinner wall surface of the communication gate inclines in such a mannerthat height W2 of the communication gate decreases from the first regionA side toward the second region B side. Thus, the first substratesurface forming the upper inner wall surface of the communication gateis gradually inclined in such a manner that the groove depth isinitially identical to that of first region A and then graduallydecreases, and accordingly the liquid reagent can be successfully flownfrom the first region A side toward the second region B side withoutleaving liquid.

In the case where the microchip is structured using the first substratehaving the groove shape as shown in FIG. 4, depth W4 of the grooveforming first region A may be approximately 1.0 to 5.0 mm and preferablyapproximately 1.5 to 2.5 mm, for example. Groove depth W5 of inclinedsurface M at the end abutting on the second region may be approximately0.1 to 0.4 mm and preferably approximately 0.2 to 0.3 mm, for example.

In the example shown in FIG. 2, partition 130 has two communicationgates 131, and these communication gates are disposed at the twoopposing ends of partition 130, respectively. In the case where theportion of the liquid reagent located in the region opposite topartition 130 with respect to liquid reagent inlet 113 in first region Ais to be caused to flow through the communication gates into secondregion B by applying a centrifugal force, the liquid reagent is morelikely to flow along the sidewall surface of first region A to reachpartition 130 because of the influence of the surface tension of theliquid reagent. Therefore, the communication gates may be disposed atthe two opposing ends of the partition, namely along the sidewallsurface of the liquid reagent retaining portion, so that the liquidreagent can be successfully discharged. Further, the cross section ofpartition 130 in the direction parallel to the surface (groove-formedsurface) of first substrate 100 has a V-shape protruding toward firstregion A. The partition having such a shape can be used to guide theliquid reagent having reached any portion other than the portions wherecommunication gates 131 of partition 130 are formed, towardcommunication gates 131. Thus, the liquid reagent can be prevented fromremaining around partition 130. The cross-sectional shape of partition130 is not limited to the V shape, and may be the U shape protrudingtoward first region A. A part of partition 130 may have such a V or Ushape.

Thickness W3 of partition 130 is not particularly limited to a specificone, and may be approximately 0.5 to 1.5 mm, and preferablyapproximately 0.5 to 1.0 mm, for example. Thickness W3 of partition 130may not necessarily be constant.

The position of partition 130 in liquid reagent retaining portion 104 isnot particularly limited to a specific one, as long as the partition isdisposed between liquid reagent inlet 113 and the inside opening(opening abutting on first region A) of outflow channel 120. In terms ofsecuring a space for temporarily accommodating the liquid reagentflowing out from communication gate 131 and for preventing the liquidreagent from occupying outflow channel 120, it is preferable that secondregion B between partition 130 and outflow channel 120 has an adequatevolume.

Outflow channel 120 may have a square or rectangular cross section likecommunication gate 131. In order to allow outflow channel 120 to havethe valve function, preferably the width and height of outflow channel120 are each 0.1 to 0.4 mm, and more preferably 0.2 to 0.3 mm. Thecross-sectional shape of the outflow channel may be identical or mayvary along the whole dimension in the direction of length. Further,outflow channel 120 and communication gate 131 may be identical to ordifferent from each other in width and height.

The microchip of the present embodiment may be modified in variousmanners in addition to the above-described ones as long as themodifications fall within what is intended by the present invention. Themodifications may include the following ones.

(1) Like a liquid reagent retaining portion 504 shown in FIG. 5, apartition 530 may have a cross section parallel to the surface(groove-formed surface) of the first substrate that is a V or U shapeprotruding toward second region B. Any appropriate cross-sectional shapelike the above-described one may be selected for the purpose ofproviding the partition within the limited space.

(2) As shown in FIG. 5 and FIG. 6 (schematic cross-sectional view of apartition and its peripheral portion along line III-III′ shown in FIG.5), on the bottom of the groove of the first substrate that forms theupper inner wall surface of first region A, the depth of the groovesection in region X adjacent to a communication gate 531 may becomeshallower toward communication gate 531. In the microchip using thefirst substrate having the above-described incline structure, the upperinner wall surface of first region A includes the portion in region X ofthe liquid reagent retaining portion where the height decreases towardcommunication gate 531. Thus, the bottom of the groove in region X isinclined in such a manner that the depth which is initially identical tothat of first region A other than region X gradually decreases, so thatthe liquid reagent can be successfully flown out from first region Ainto second region B without leaving the liquid. In the case whereregion X has the inclined structure, the bottom of the groove formingthe upper inner wall surface of the communication gate may notnecessarily have the inclined structure.

(3) The number of the communication gates is not limited to two, and onecommunication gate may be provided. As long as one communication gatehaving the valve function is provided, the liquid reagent retainingability can be improved. It should be noted, however, that twocommunication gates are preferably provided in order to prevent theliquid reagent from being moved due to impact to occupy all of thecommunication gates. Three or more communication gates may be provided.

The liquid reagent retaining portion may not necessarily have theoutflow channel, and may include only a liquid reagent outlet forallowing the liquid reagent to flow out. In terms of further preventingthe liquid reagent retaining ability, however, it is preferable toprovide the outflow channel.

An operational method of the microchip in the present embodiment usingthe first substrate shown in FIGS. 1 and 2 will be generally described.Here, the operational method described below is an exemplary one, and isnot limited to the method as described. First, a sample tube into whicha sample of the whole blood is taken is inserted into sample tube mountportion 101. Next, a centrifugal force in the leftward direction withrespect to FIG. 1 (hereinafter simply referred to as leftwardcentrifugal force, centrifugal forces in other directions will be calledsimilarly below) is applied to the microchip to draw out the whole-bloodsample in the sample tube. After this, a downward centrifugal force isapplied to cause the whole-blood sample to be introduced into plasmaseparating portion 102 where the blood is separated into a blood plasmacomponent and a blood cell component by centrifugal separation. When thewhole-blood sample is introduced into plasma separating portion 102, anoverflowing whole-blood sample portion is received in a waste liquidstorage 115. The downward centrifugal force also causes a liquid reagentS1 retained in first region A of liquid reagent retaining portion 104 toflow out into second region B through communication gates 131 andfurther flow through outflow channel 120 to be introduced into a liquidreagent measuring portion 106 where the liquid reagent is measured.

Subsequently, the separated blood plasma component is introduced into asample measuring portion 103 by a rightward centrifugal force. At thistime, the measured liquid reagent S1 is moved to mixing portion 109, anda liquid reagent S2 in liquid reagent retaining portion 105 isdischarged through the communication gates from the outflow channel.

Next, a downward centrifugal force is applied. Accordingly, the measuredblood plasma component and the measured liquid reagent S1 are mixed inmixing portion 108, and liquid reagent S2 is measured by liquid reagentmeasuring portion 107. Then, rightward, downward and rightwardcentrifugal forces are applied successively to move the liquid mixturebetween mixture portions 108 and 109 so that the liquid mixture issufficiently mixed.

Next, an upward centrifugal force is applied. Accordingly, the liquidmixture of liquid reagent S1 and the blood plasma component is mixedwith the measured liquid reagent S2 in a mixing portion 110. Then,leftward, upward, leftward, and upward centrifugal forces aresuccessively applied to move the liquid mixture between mixing portions110 and 111 so that the liquid mixture is sufficiently mixed.

Finally, a rightward centrifugal force is applied to introduce theliquid mixture in mixing portion 110 into detecting portion 112. Theliquid mixture in detecting portion 112 undergoes optical measurement bymeans of light applied to detecting portion 112. For example, theintensity of the transmitted light is measured.

Second Embodiment

A microchip of the present embodiment will be described in connectionwith a preferred example thereof. While characteristic features of themicrochip of the present embodiment will be chiefly described below,other features are similar to those of the first embodiment as describedabove.

FIG. 7 is a top view showing a preferred example of the microchip of thepresent embodiment, formed by superposing and bonding a first substrate700 having a groove in a surface on a second substrate (not shown). Inthe microchip shown in FIG. 7, first substrate 700 is bonded to thesecond substrate (not shown) in such a manner that the groove-formedsurface of the first substrate is located opposite to the secondsubstrate. While FIG. 7 shows the surface of first substrate 700 that isopposite to the groove-formed surface thereof, a groove pattern isindicated by the solid line for convenience of description. In themicrochip shown in FIG. 7, the second substrate is identical or similarin outline form to first substrate 700. First substrate 700 and thesecond substrate are respectively a plastic transparent substrate and aplastic black substrate, for example.

The microchip shown in FIG. 7 is chiefly constituted of a sample tubemount portion 701 for incorporating a sample tube such as capillarycontaining the whole blood taken from a subject, a separating portion702 for separating the whole blood drawn from the sample tube into ablood cell component and a blood plasma component, a blood cellmeasuring portion 703 for measuring the separated blood cell component,three liquid reagent retaining portions 704, 705 and 706 serving asfluid retaining reservoirs for retaining a liquid reagent, liquidreagent containers 707 and 708 serving as fluid containing reservoirsprovided adjacent to liquid reagent retaining portions 705 and 706respectively for temporarily containing the liquid reagent, three liquidreagent measuring portions 709, 710 and 711 for measuring the liquidreagent, a first mixing portion 712 for mixing the blood cell componentwith the liquid reagent, a liquid mixture measuring portion 713 formeasuring the liquid mixture of the blood cell component and the liquidreagent, a second mixing portion 714 for mixing the liquid mixture ofthe blood cell component and the liquid reagent with another liquidreagent, and a detecting portion 715 where a test and an analysis areconducted for the finally obtained liquid mixture. The three liquidreagent retaining portions 704, 705 and 706 respectively include liquidreagent inlets 716, 717 and 718 for injecting the liquid reagent intothe corresponding liquid reagent retaining portions. Liquid reagentinlets 716, 717 and 718 that are fluid inlets are through openingsextending through first substrate 700 in the thickness direction. In thefollowing, respective liquid reagents injected via the liquid reagentinlets and retained in respective liquid reagent retaining portions 704,705 and 706 will be referred to as liquid reagents R0, R1 and R2respectively.

As seen from above, the fluid circuit of the microchip shown in FIG. 7has a structure appropriate for mixing the blood cell componentseparated from the whole blood with liquid reagents R0, R1 and R2 inthis order and performing a test and an analysis such as opticalmeasurement on the resultant liquid mixture. In the following, a liquidreagent retaining portion and a peripheral portion thereof that is acharacteristic feature of the present embodiment will be described indetail in connection with liquid reagent retaining portion 705 as anexample.

FIG. 8 is an enlarged top view of liquid reagent retaining portion 705and its peripheral portion of the microchip shown in FIG. 7. As shown inFIG. 8, in the microchip shown in FIG. 7, liquid reagent container 707for temporarily containing liquid reagent R1 is provided adjacent toliquid reagent retaining portion 705 retaining liquid reagent R1.Specifically, a first outflow channel 720 is provided for allowingliquid reagent R1 injected from liquid reagent inlet 717 and retained inliquid reagent retaining portion 705 to flow out. One end of firstoutflow channel 720 is connected to an end of liquid reagent retainingportion 705 and the other end thereof is connected to liquid reagentcontainer 707. Liquid reagent container 707 is disposed to allow liquidreagent R1 flowing out from liquid reagent retaining portion 705 to betemporarily contained in liquid reagent container 707. Liquid reagentcontainer 707 is formed by a region defined by a part of a wall M′forming liquid reagent retaining portion 705 and a wall N located tosurround the peripheral portion of first outflow channel 720.

Liquid reagent container 707 has an opening (opening X′ in FIG. 8)separately from the opening at the portion connected to first outflowchannel 720. To opening X′, a second outflow channel 721 is connectedfor allowing liquid reagent R1 to flow out from liquid reagent container707. The other end of second outflow channel 721 is directly connectedto liquid reagent measuring portion 710. Thus, as a centrifugal force inan appropriate direction is applied (leftward centrifugal force in FIG.8 for example), liquid reagent R1 is discharged from liquid reagentcontainer 707 and liquid reagent R1 is then introduced into liquidreagent measuring portion 710 by the centrifugal force and measured.

Since liquid reagent container 707 having the above-described structureand capable of temporarily containing liquid reagent R1 flowing out fromliquid reagent retaining portion 705 is provided, even if an externalimpact is exerted on the microchip or the internal pressure of liquidreagent retaining portion 705 increases, for example, liquid reagent R1can be prevented from flowing out into liquid reagent measuring portion710. Specifically, first outflow channel 720 is a fine flow channel anditself functions as a valve, and thus outflow from liquid reagentretaining portion 705 into liquid reagent container 707 is relativelyless likely to occur in this structure. If, however, the microchip issubjected to an external impact, unintended outflow could occur. Forexample, there could be the case where liquid reagent R1 is dischargedfrom liquid reagent retaining portion 705 by the impact. There couldalso be the case where impact causes liquid reagent R1 to move to occupythe opening of first outflow channel 720 and, when a subsequent increasein environmental temperature causes the internal pressure of liquidreagent retaining portion 705 to increase, liquid reagent R1 occupyingthe opening could be discharged. Even in these cases, liquid reagentcontainer 707 is provided to allow liquid reagent R1 flowing out fromliquid reagent retaining portion 705 to be contained in liquid reagentcontainer 707, so that liquid reagent R1 can be prevented from flowingout into liquid reagent measuring portion 710. The function of valvehere refers to the function that undesired discharge of the liquidreagent is prevented while desired discharge can be done by applicationof a centrifugal force with a predetermined strength. Further, sinceliquid reagent R1 is retained in a nearly sealed state until themicrochip is used, quality degradation is less likely to occur.

If the microchip contains a plurality of different types of liquidreagents, the liquid reagent container may serve to temporarily keep thereagent on standby. Accordingly, the liquid reagents can be introducedat appropriate timings respectively into the measuring portions and canbe mixed at proper timings respectively with the sample. The microchiphaving such a liquid reagent container is particularly useful in thecase where a plurality of different types of liquid reagents have to bemixed successively in an appropriate order with the sample.

In the microchip shown in FIGS. 7 and 8, second outflow channel 721connecting liquid reagent container 707 and liquid reagent measuringportion 710 also has the valve function, like first outflow channel 720.Therefore, as a centrifugal force with a predetermined strength isapplied, liquid reagent R1 contained in liquid reagent container 707 isintroduced into liquid reagent measuring portion 710. Liquid reagentretaining portion 705 may not necessarily have first outflow channel720. Instead of the outflow channel, an opening such as through openingextending through wall M′ which forms liquid reagent retaining portion705 may be provided to connect liquid reagent retaining portion 705 andliquid reagent container 707 by the opening. Likewise, liquid reagentcontainer 707 may not necessarily have second outflow channel 720.Instead, an opening such as through opening extending through wall Nwhich forms liquid reagent container 707 may be provided to connectliquid reagent container 707 and liquid reagent measuring portion 710 bythe opening. It should be noted, however, that preferably these portionsare connected by the outflow channels for allowing the valve function tosuccessfully work. In order to effect a favorable valve function, thewidth of first outflow channel 720 and second outflow channel 721 ispreferably approximately 0.1 to 0.5 mm and more preferably approximately0.3 mm. The length of first outflow channel 720 and second outflowchannel 721 is preferably approximately 0.6 to 3.0 mm and morepreferably approximately 1.2 to 2.0 mm.

Second outflow channel 721 preferably extends in a direction differentfrom first outflow channel 720 as shown in FIG. 8. More preferably,first outflow channel 720 and second outflow channel 721 are disposed insuch a manner that the direction of the flow of liquid reagent R1 infirst outflow channel 720 and that of liquid reagent R1 in secondoutflow channel 721 make an angle of 90° to 180°. Accordingly, in thecase where liquid reagent container 707 has the function of keeping theliquid reagent on standby as described above, liquid reagent R1 can beprevented from flowing directly into liquid reagent measuring portion710 without being contained in liquid regent container 707, by the samecentrifugal force as the centrifugal force for moving liquid reagent R1from liquid reagent retaining portion 705 to liquid reagent container707.

Second outflow channel 721 and opening X to which second outflow channel721 is connected are preferably disposed at the wall forming liquidreagent container 707, at a position relatively closer to liquid reagentretaining portion 705. More preferably, second outflow channel 721 andopening X′ are provided along wall M′ forming liquid reagent retainingportion 705. Thus, the liquid reagent retaining portion and itsperipheral portion can be more integrated.

In the present embodiment, a partition may be provided in the liquidreagent retaining portion for dividing the liquid reagent retainingportion into two sections. FIG. 9 is an enlarged top view of a liquidreagent retaining portion and its peripheral portion in anotherpreferred example of the microchip in the present embodiment. In aliquid reagent retaining portion 905 shown in FIG. 9, a partition 900 isprovided that divides liquid reagent retaining portion 905 into a firstregion A including a liquid reagent inlet 917 and a second region Bincluding a first outflow channel 920. Partition 900 has twocommunication gates 910 at the two opposing ends of partition 900respectively, for allowing communication between first region A andsecond region B. A cross section of partition 900 in the directionparallel to the groove-formed surface of the first substrate is in theU-shape protruding toward first region A.

Here, a liquid reagent container 907 for temporarily containing theliquid reagent is provided adjacent to liquid reagent retaining portion905. Liquid reagent container 907 is connected to a second outflowchannel 921 for allowing the liquid reagent to flow out. The other endof second outflow channel 921 is connected to a liquid reagent measuringportion 930. These components are similar to those shown in FIG. 8.

Partition 900 having such communication gates 910 is thus provided inliquid reagent retaining portion 905. Then, when liquid reagent R1 isinjected into liquid reagent retaining portion 905, liquid reagent R1injected from liquid reagent inlet 917 and contained in first region Ais less likely to flow out into second region B even if impact isexerted on the microchip, since two communication gates 910 function asvalves. Namely, the liquid reagent retaining portion including such apartition has a further superior ability to retain the liquid reagentagainst impact, and unintended outflow of the liquid reagent from theliquid reagent retaining portion due to impact can be more effectivelysuppressed or prevented.

Since partition 910 is disposed, liquid reagent RI when injected intoliquid reagent retaining portion 905 can be suppressed or prevented fromoccupying the inside opening of first outflow channel 920 (the openingabutting on liquid reagent retaining portion 905). Further, it can besuppressed or prevented that the liquid reagent is caused to move due toimpact to occupy the inside opening of first outflow channel 920, andthus liquid reagent R1 occupying the inside opening can be suppressed orprevented from flowing out from liquid reagent retaining portion 905 dueto an increase of the internal pressure of liquid reagent retainingportion 905 caused by an increase of the environmental temperature forexample.

The cross-sectional shape of communication gate 910 is not particularlylimited to a specific one, and may be square or rectangular for example.In order to allow communication gate 910 to have the valve function, thewidth and the height of communication gate 910 are each preferably 0.1to 0.5 mm, and more preferably 0.2 to 0.3 mm. If two or morecommunication gates are provided like the example shown in FIG. 9,respective cross-sectional shapes of the communication gates may beidentical to or different from each other. Further, the cross-sectionalshape of the communication gate may be identical or may vary along thewhole dimension in the direction of the length (direction of the lengthrefers to the direction of the thickness of partition 900 shown in FIG.9). Specifically, in the former case (the cross-sectional shape ofcommunication gate 910 is identical along the whole dimension in thedirection of the thickness), the cross sectional shape of communicationgate 910 at the end abutting on first region A, the cross sectionalshape thereof at the other end abutting on second region B and thecross-sectional shape thereof between these ends are all identical orsubstantially identical to each other. The communication gate having theabove-described shape is preferable because such a communication gate isrelatively easy to process.

In the case where the cross-sectional shape of the communication gatevaries in the direction of the length, (i) the height of thecommunication gate is constant while the width continuously decreases orincreases, or (ii) the width of the communication gate is constant whilethe height continuously decreases or increases, for example. A morespecific example of case (ii) above is as follows. On the groove-formedsurface of the first substrate, the bottom of the groove thatconstitutes a part of the inner wall surface of communication gate 910becomes gradually shallower from first region A toward second region Bto form an inclined surface (the inclined surface is the surface formingthe upper inner wall surface of the communication gate when the firstsubstrate is superposed on the second substrate (namely it is supposedhere that the first substrate is located on the “upper side” withrespect to the second substrate)). In this case, the upper inner wallsurface of the communication gate inclines in such a manner that theheight of the communication gate decreases from the first region A sidetoward the second region B side. Thus, the first substrate surfaceforming the upper inner wall surface of the communication gate isgradually inclined in such a manner that the groove depth is initiallyidentical to that of first region A and then gradually decreases, andaccordingly the liquid reagent can be successfully flown from the firstregion A side toward the second region B side without leaving theliquid.

In the example shown in FIG. 9, partition 900 has two communicationgates 910, and these communication gates are disposed at the twoopposing ends of partition 900, respectively. In the case where theportion of liquid reagent R1 located in the region opposite to partition900 with respect to liquid reagent inlet 917 in first region A is to becaused to flow through communication gates 910 into second region B byapplying a centrifugal force, liquid reagent R1 is more likely to flowalong the sidewall surface of first region A to reach partition 900because of the influence of the surface tension of the liquid reagent.Therefore, the communication gates may be disposed at the two opposingends of the partition, namely along the sidewall surface of the liquidreagent retaining portion, so that liquid reagent R1 can be successfullydischarged.

Further, the cross section of partition 900 in the direction parallel tothe groove-formed surface of the first substrate has a U shapeprotruding toward first region A. The partition having such a shape canbe used to guide liquid reagent R1 having reached any portion other thanthe portions where communication gates 910 of partition 900 are formed,toward communication gates 910. Thus, the liquid reagent can beprevented from remaining around partition 900. The cross-sectional shapeof partition 900 is not limited to the U shape, and may be a V shapeprotruding toward first region A. A part of partition 900 may have sucha V or U shape.

The thickness of partition 900 is not particularly limited to a specificone, and may be approximately 0.5 to 1.5 mm, and preferablyapproximately 0.5 to 1.0 mm, for example. The thickness of partition 900may not necessarily be constant.

The position of partition 900 in liquid reagent retaining portion 905 isnot particularly limited to a specific one, as long as the partition isdisposed between liquid reagent inlet 917 and the inside opening offirst outflow channel 920. In terms of securing a space for temporarilyaccommodating liquid reagent R1 flowing out from communication gate 910and for preventing liquid reagent R1 from occupying first outflowchannel 920, it is preferable that second region B between partition 900and first outflow channel 920 has an adequate volume.

Partition 900 may have a cross section parallel to the groove-formedsurface of the first substrate that is a V or U-shape protruding towardsecond region B. Any appropriate cross-sectional shape like theabove-described one may be selected for the purpose of providing thepartition within the limited space. The number of the communicationgates is not limited to two, and one communication gate may be provided.As long as one communication gate having the valve function is provided,the liquid reagent retaining ability can be improved. It should benoted, however, that two communication gates are preferably provided inorder to prevent the liquid reagent from being moved due to impact tooccupy all of the communication gates. Three or more communication gatesmay be provided.

An operational method of the microchip shown in FIG. 7 will be generallydescribed. Here, the operational method described below is an exemplaryone, and is not limited to the method as described. First, a sample tubeinto which a sample of the whole blood is taken is inserted into sampletube mount portion 701. Next, a centrifugal force in the leftwarddirection with respect to FIG. 7 (hereinafter simply referred to asleftward centrifugal force, centrifugal forces in other directions willbe called similarly below) is applied to the microchip to draw out thewhole-blood sample in the sample tube. After this, a downwardcentrifugal force is applied to cause the whole-blood sample to beintroduced into separating portion 702 where the blood is separated intoa blood plasma component and a blood cell component by centrifugalseparation. Next, a leftward centrifugal force is applied to remove theblood plasma component in the upper layer. At this time, the removedblood plasma component is received in a region “a.” Subsequently, adownward centrifugal force is applied to smooth the surface of the bloodcell component in separating portion 702, and move the removed bloodplasma component to a region “b.” Next, a rightward centrifugal force isapplied to introduce liquid reagent R0 in liquid reagent retainingportion 704 into liquid reagent measuring portion 709 to measure theliquid reagent. This centrifugal force causes liquid reagent R1 inliquid reagent retaining portion 705 and liquid reagent R2 in liquidreagent retaining portion 706 to move to liquid reagent containers 707and 708 respectively. This centrifugal force also causes the blood cellcomponent in separating portion 702 to be introduced into blood cellmeasuring portion 703 and measured therein.

Next, a downward centrifugal force is applied to mix the measured bloodcell component with liquid reagent R0 in first mixing portion 712 toproduce a liquid mixture. This centrifugal force causes liquid reagentR2 in liquid reagent container 708 to be measured in liquid reagentmeasuring portion 711. Then, rightward, downward, leftward, and downwardcentrifugal forces are successively applied to sufficiently mix theliquid mixture. This leftward centrifugal force allows liquid reagent R1in liquid reagent container 707 to be measured by liquid reagentmeasuring portion 710. Further, the last downward centrifugal forcecauses the measured liquid reagent R1 to move to second mixing portion714.

Next, a leftward centrifugal force is applied and thereafter anupper-leftward centrifugal force and then a leftward centrifugal forceare applied to introduce the supernatant portion of the liquid mixturein first mixing portion 712 into liquid mixture measuring portion 713and measured therein. Then, a downward centrifugal force is applied tomix the measured liquid mixture with liquid reagent R1 in second mixingportion 714. Subsequently, leftward and downward centrifugal forces aresuccessively applied to sufficiently mix the liquid mixture. In thestate where the downward centrifugal force is applied, the measuredliquid reagent R2 is located in a region “c.” Next, a rightwardcentrifugal force is applied to mix the liquid mixture with liquidreagent R2 in detecting portion 715. Further, a downward centrifugalforce is applied to sufficiently mix the liquid mixture with the liquidreagent. Finally, a rightward centrifugal force is applied so that theliquid mixture is contained in detecting portion 715. Light is appliedto detecting portion 715 and optical measurement is performed such asmeasurement of the intensity of the transmitted light, for example.

Third Embodiment

A microchip of the present embodiment will be described in connectionwith some preferred examples thereof. While characteristic features ofthe microchip of the present embodiment will be chiefly described below,other features are similar to those of the first embodiment as describedabove.

FIG. 10 is a top view showing a preferred example of a microchip of thepresent embodiment, formed by superposing and bonding a first substrate1000 having a groove formed in a surface onto a second substrate 200(not shown in FIG. 10) and showing a fluid circuit of the microchip. Inthe microchip shown in FIG. 10, first substrate 1000 is bonded to secondsubstrate 200 (not shown) in such a manner that the groove-formedsurface of the first substrate is located opposite to the secondsubstrate. While FIG. 10 shows the surface of first substrate 1000 thatis opposite to the groove-formed surface thereof, a groove pattern isindicated by the solid line for convenience of description. In themicrochip shown in FIG. 10, second substrate 200 is identical or similarin outline form to first substrate 1000. First substrate 1000 and secondsubstrate 200 are respectively a plastic transparent substrate and aplastic black substrate, for example. The hatching in some regions ofFIG. 10 means that the region indicated by the hatching is tapered(specifically the bottom of the groove in the hatched region is inclinedrelative to the bottom of the groove in an adjacent region). The same isapplied as well to the hatching in FIG. 11 described below.

A fluid circuit of the microchip shown in FIG. 10 is chiefly constitutedof a sample tube mount portion 1001 for incorporating a sample tube suchas capillary containing the whole blood taken from a subject, aseparating portion 1002 for separating the whole blood drawn from thesample tube into a blood cell component and a blood plasma component, ablood cell measuring portion 1003 for measuring the separated blood cellcomponent, three liquid reagent retaining portions 1004, 1005 and 1006serving as fluid retaining reservoirs for retaining a liquid reagent,liquid reagent containers 1007 and 1008 serving as fluid containingreservoirs provided adjacent to liquid reagent retaining portions 1005and 1006 respectively for temporarily containing the liquid reagent,three liquid reagent measuring portions 1009, 1010 and 1011 formeasuring the liquid reagent, a first mixing portion 1012 for mixing theblood cell component with the liquid reagent, a liquid mixture measuringportion 1013 for measuring the liquid mixture of the blood cellcomponent and the liquid reagent, a second mixing portion 1014 formixing the liquid mixture of the blood cell component and the liquidreagent with another liquid reagent, and a detecting portion 1015 wherea test and an analysis are conducted for the finally obtained liquidmixture. The three liquid reagent retaining portions 1004, 1005 and 1006respectively include liquid reagent inlets 1016, 1017 and 1018 forinjecting the liquid reagent into the corresponding liquid reagentretaining portions. Liquid reagent inlets 1016, 1017 and 1018 that arefluid inlets are through openings extending through first substrate 1000in the thickness direction. In the following, respective liquid reagentsinjected via the liquid reagent inlets and retained in respective liquidreagent retaining portions 1004, 1005 and 1006 will be referred to asliquid reagents R0, R1 and R2 respectively.

As seen from above, the fluid circuit of the microchip shown in FIG. 10has a structure appropriate for mixing the blood cell componentseparated from the whole blood with liquid reagents R0, R1 and R2 inthis order and performing a test and an analysis such as opticalmeasurement on the resultant liquid mixture. In the following, a liquidreagent retaining portion serving as a fluid retaining reservoir that isa characteristic feature of the present embodiment will be described indetail in connection with liquid reagent retaining portion 1005 as anexample.

FIG. 11 is an enlarged top view of liquid reagent retaining portion 1005of the microchip shown in FIG. 10. FIG. 12 is a schematiccross-sectional view along line XII-XII shown in FIG. 11. FIG. 12 showsfirst substrate 1000 together with second substrate 200 bonded to firstsubstrate 1000.

Liquid reagent retaining portion 1005 of the microchip shown in FIGS. 11and 12 includes liquid reagent inlet 1017 composed of a through openingextending from a surface of the microchip (surface of first substrate1000) to liquid reagent retaining portion 1005, and a reagent outlet1020 serving as a fluid outlet for allowing liquid reagent R1 to flowout from liquid reagent retaining portion 1005. Liquid reagent retainingportion 1005 also includes a partition 1030 therein for dividing liquidreagent retaining portion 1005 into two sections, namely a first regionA where the through opening forming liquid reagent inlet 1017 isprovided and the liquid reagent is introduced and contained, and asecond region B where reagent outlet 1020 is provided.

Partition 1030 as shown in FIG. 12 is formed by a protrusion 1031provided on the second-substrate 200-side surface of first substrate1000, and a communication gate 1032 formed by a space between the flatsurface of the leading end of protrusion 1031 and the opposite surface(first-substrate 1000-side surface) of second substrate 200, forallowing communication between first region A and second region B.

As liquid reagent R1 is injected from liquid reagent inlet 1017 intoliquid reagent retaining portion 1005 having the above-describedstructure, liquid reagent R1 is received in first region A. In themicrochip having the above-described structure in which liquid reagentR1 is contained in first region A, liquid reagent R1 is less likely toflow out into second region B even if external impact is exerted or theinternal pressure of first region A in liquid reagent retaining portion1005 increases due to a change of the environmental temperature forexample. Therefore, liquid reagent R1 contained in first region A can beeffectively prevented from flowing out from liquid reagent retainingportion 1005. In other words, the liquid reagent retaining portion inthe microchip of the present embodiment has an excellent reagentretaining ability against impact and an increase of the internalpressure of the liquid reagent retaining portion. While the liquidreagent retaining portion has a relatively simple structure, the liquidreagent retaining portion can effectively prevent unintended outflow ofthe liquid reagent from the liquid reagent retaining portion due toimpact and the increase of the internal pressure of the liquid reagentretaining portion. Partition 1030 having communication gate 1032 has thefunction of “valve.” If outflow is not desired, partition 1030 serves tokeep liquid reagent R1 from flowing out from first region A. If outflowis desired, partition 1030 allows liquid reagent R1 to flow out fromfirst region A by application of a centrifugal force with apredetermined strength.

In the microchip shown in FIGS. 11 and 12, reagent outlet 1020 also hasthe function of valve. Liquid reagent retaining portion 1005 thereforehas the two-stage valve. Since reagent outlet 1020 thus has the valvefunction, even if impact is exerted to cause liquid reagent R1 to flowout from communication gate 1032 into second region B, the possibilitythat liquid reagent R1 flows out from liquid reagent retaining portion1005 can be made extremely low.

Further, since partition 1030 is provided, when liquid reagent R1 isinjected into liquid reagent retaining portion 1005, liquid reagent R1can be suppressed or prevented from occupying the inside opening(opening abutting on first region A) of reagent outlet 1020. Further,liquid reagent R1 can be suppressed or prevented from moving due toimpact to occupy the inside opening of reagent outlet 1020 as describedabove. It can therefore be suppressed or prevented that liquid reagentR1 occupying the inside opening is caused to flow out from the liquidreagent retaining portion due to an increase of the internal pressure inthe liquid reagent retaining portion due to an increase of theenvironmental temperature, for example.

Here, a part of partition 1030 includes a curved portion 1033 formed ofa wall in the shape of a curve as shown in FIG. 11, as seen from thesurface of the microchip (the surface of first substrate 1000 forexample) (namely when the microchip is seen from the upper surface sidein the direction of thickness of the microchip). Specifically,protrusion 1031 forming partition 1030 includes arc-shaped curvedportion 1033 at a central portion, and straight walls formed at the twoopposing ends of curved portion 1033. Since the partition thus has acurved portion, when the liquid reagent in first region A is caused tocontact the partition under a certain pressure (for example impact onthe microchip or an increase of the internal pressure in first region A)for example, the pressure exerted by the liquid reagent can bedispersed. Further, in the case where the liquid reagent is a circularbulk, the contact area between the partition and the liquid reagent canbe increased, so that the liquid-reagent-retaining capability can befurther improved. In order to further improve theliquid-reagent-retaining capability, it is preferable that the partitionhaving the curved portion protrudes toward second region B as shown inFIG. 11.

The shape of the curved portion is not particularly limited to aspecific one. The curved portion is preferably arc-shaped, since the arcshape can more efficiently disperse the pressure and since the liquidreagent contained in the liquid reagent retaining portion is usuallywater-based reagent and forming a substantially circular bulk solutionin the first region A. The curved portion in the shape of an arc canmore efficiently disperse the pressure from the liquid reagent and canincrease the contact area between the partition and the liquid reagentand therefore can further improve the liquid-reagent-retainingcapability.

In the case where the curved portion has the shape of an arc, the radiusof curvature of the arc is not particularly limited to a specific one,and may be approximately 2 to 5 mm for example. It is preferable thatthe radius of curvature is adjusted according to the amount of theliquid reagent contained in the liquid reagent retaining portion.Specifically, the radius of curvature of the arc is identical orsubstantially identical to the radius of the circular bulk solutionshown by the liquid reagent in first region A.

Referring to FIG. 12, height S of communication gate 1032 is preferablyapproximately 0.1 to 0.2 mm. If height S is smaller than 0.1 mm, thefirst substrate and the second substrate could be welded together in theregion where the communication gate is to be formed, in the process ofmanufacturing the microchip, and the liquid reagent may not flow outfrom first region A even when a centrifugal force is applied. If heightS is larger than 0.2 mm, partition 1030 cannot have an appropriate valvefunction, so that the liquid reagent could be caused to flow out fromfirst region A due to impact or increase of the internal pressure.Length Y of communication gate 1032 is not particularly limited to aspecific one as long as partition 1030 can have an appropriate valvefunction, and may be approximately 0.2 to 2 mm and preferablyapproximately 0.5 to 1.0, for example. In order to discharge the liquidreagent without leaving the liquid when a centrifugal force is applied,preferably the flat surface at the leading end of protrusion 1031 andthe opposite surface of second substrate 200 (first-substrate 1000-sidesurface) are preferably parallel or substantially parallel to eachother.

Preferably, the side surface of partition 1030 that is located on firstregion A side has an inclined surface which is inclined with respect tothe thickness direction of the microchip. Specifically, protrusion 1031forming partition 1030 has an inclined surface F on first region A sideas shown in FIGS. 11 and 12. Since such inclined surface F is provided,the whole amount of the liquid reagent can be smoothly flown out fromfirst region A when a predetermined centrifugal force is applied for thepurpose of causing the liquid reagent to flow out therefrom, and thusthe liquid reagent can be prevented from remaining in first region A.The angle of inclination of inclined surface F, namely the angle formedby the surface of first substrate 1000 that forms first region A andinclined surface F (angle α in FIG. 12) is preferably an obtuse angle,and more preferably 95° or more. In contrast, the angle formed by thesurface of first substrate 1000 that forms second region B and the sideof protrusion 1031 on second region B side (angle β in FIG. 12) is notparticularly limited to a specific one, and may be approximately 90° oran acute angle, Width L (see FIG. 11) of protrusion 1031 in the regionwhere inclined surface F is formed is preferably set relatively long,since the liquid reagent retaining capability is further improved whenthe contact area where the liquid reagent contacts protrusion 1031 islarger. Width L may be approximately 1 to 3 mm for example.

The position of partition 1030 in liquid reagent retaining portion 1005is not particularly limited to a specific one, as long as the partitionis disposed between liquid reagent inlet 1017 and liquid reagent outlet1020.

In liquid reagent retaining portions 1004 and 1006, similar partitionsare provided as well (see FIG. 10), while which will not be described indetail. The partition provided in liquid reagent retaining portion 1006is formed of a linear protrusion as seen from the surface of themicrochip.

In the microchip shown in FIG. 10, liquid reagent container 1007 fortemporarily containing liquid reagent R1 is provided adjacent to liquidreagent retaining portion 1005 retaining liquid reagent R1.Specifically, liquid reagent container 1007 is connected to an end ofreagent outlet 1020 of liquid reagent retaining portion 1005, and isdisposed in such a manner that liquid reagent R1 flowing out from liquidreagent retaining portion 1005 is temporarily contained in liquidreagent container 1007. Similarly, liquid reagent container 1008 isprovided adjacent to liquid reagent retaining portion 1006.

Liquid reagent container 1007 includes an opening in addition to the oneat the portion where liquid reagent container 1007 is connected toreagent outlet 1020. To the opening, liquid reagent measuring portion1010 is connected. Thus, when a centrifugal force in an appropriatedirection (leftward centrifugal direction with respect to FIG. 10 forexample) is applied to cause liquid reagent R1 to be discharged fromliquid reagent container 1007, liquid reagent R1 is introduced by thecentrifugal force into liquid reagent measuring portion 1010 where thereagent is measured.

Since liquid reagent container 1007 capable of temporarily containingliquid reagent R1 which flows out from liquid reagent retaining portion1005 is provided, even if liquid reagent R1 flows out from liquidreagent retaining portion 1005 due to impact on the microchip or anincrease of the internal pressure of liquid reagent retaining portion1005, liquid reagent R1 can be prevented from flowing out into liquidreagent measuring portion 1010. Further, in the case where the microchipcontains therein a plurality of different liquid reagents, such a liquidreagent container can perform the function of temporarily keeping theliquid reagent on standby. Thus, each of the liquid reagents can beintroduced at an appropriate timing into the measuring portion and canbe mixed with a sample at an appropriate timing. The microchip havingsuch a liquid reagent container is particularly useful in the case wherea plurality of different liquid reagents have to be mixed with a samplesuccessively in an appropriate order.

An operational method of the microchip shown in FIG. 10 will begenerally described. Here, the operational method described below is anexemplary one, and is not limited to the method as described. First, asample tube into which a sample of the whole blood is taken is insertedinto sample tube mount portion 1001. Next, a centrifugal force in theleftward direction with respect to FIG. 10 (hereinafter simply referredto as leftward centrifugal force, centrifugal forces in other directionswill be called similarly below) is applied to the microchip to draw outthe whole-blood sample in the sample tube. After this, a downwardcentrifugal force is applied to cause the whole-blood sample to beintroduced into separating portion 1002 where the blood is separatedinto a blood plasma component and a blood cell component by centrifugalseparation. Next, a leftward centrifugal force is applied to remove theblood plasma component in the upper layer. At this time, the removedblood plasma component is contained in a region “a′.” Subsequently, adownward centrifugal force is applied to smooth the surface of the bloodcell component in separating portion 1002, and move the removed bloodplasma component to a region “b′.” Next, a rightward centrifugal forceis applied to introduce liquid reagent R0 in liquid reagent retainingportion 1004 into liquid reagent measuring portion 1009 to measure theliquid reagent. This centrifugal force causes liquid reagent R1 inliquid reagent retaining portion 1005 and liquid reagent R2 in liquidreagent retaining portion 1006 to move to liquid reagent containers 1007and 1008 respectively. This centrifugal force also causes the blood cellcomponent in separating portion 1002 to be introduced into blood cellmeasuring portion 1003 and measured therein.

Next, a downward centrifugal force is applied to mix the measured bloodcell component with liquid reagent R0 in first mixing portion 1012 toproduce a liquid mixture. This centrifugal force causes liquid reagentR2 in liquid reagent container 1008 to be measured in liquid reagentmeasuring portion 1011. Then, rightward, downward, leftward and downwardcentrifugal forces are successively applied to sufficiently mix thisliquid mixture. This leftward centrifugal force as applied allows liquidreagent R1 in liquid reagent container 1007 to be measured in liquidreagent measuring portion 1010. Further, the last downward centrifugalforce causes the measured liquid reagent R1 to move to second mixingportion 1014.

Next, a leftward centrifugal force is applied and thereafter anupper-leftward centrifugal force and then a leftward centrifugal forceare applied to introduce the supernatant portion of the liquid mixturein first mixing portion 1012 into liquid mixture measuring portion 1013and measured therein. Then, a downward centrifugal force is applied tomix the measured liquid mixture with liquid reagent R1 in second mixingportion 1014. Subsequently, leftward and downward centrifugal forces aresuccessively applied to sufficiently mix the liquid mixture. In thestate where the downward centrifugal force is applied, the measuredliquid reagent R2 is located in a region “c′.” Next, a rightwardcentrifugal force is applied to mix the liquid mixture with liquidreagent R2 in detecting portion 1015. Further, a downward centrifugalforce is applied to sufficiently mix the liquid mixture and the liquidreagent. Finally, a rightward centrifugal force is applied so that theliquid mixture is contained in detecting portion 1015. Light is appliedto detecting portion 1015 and optical measurement is performed such asmeasurement of the intensity of the transmitted light, for example.

FIG. 13 is a schematic cross-sectional view showing another example ofthe liquid reagent retaining portion included in the microchip of thepresent embodiment. Like the liquid reagent retaining portion shown inFIGS. 11 and 12, the liquid reagent retaining portion of the microchipshown in FIG. 13 includes therein a partition 330 dividing the liquidreagent retaining portion into a first region A where a through openingforming the liquid reagent inlet is provided and a second region B wherethe reagent outlet is provided. Partition 330 is constituted of aprotrusion 331 provided on the first-substrate 300-side surface of asecond substrate 400, and a communication gate 332 formed by a spacebetween a flat surface at the leading end of protrusion 331 and theopposite surface of a first substrate 300 (second-substrate 400-sidesurface), for allowing communication between first region A and secondregion B. As described above, the protrusion forming the partition maybe provided on the second substrate.

Like the liquid reagent retaining portion shown in FIGS. 11 and 12, theflat surface at the leading end of protrusion 331 and the oppositesurface of first substrate 300 (second-substrate 400-side surface) arepreferably parallel or substantially parallel to each other.

FIG. 14 is a schematic cross-sectional view showing still anotherexample of the liquid reagent retaining portion included in themicrochip of the present embodiment. Like the liquid reagent retainingportion shown in FIGS. 11 and 12, the liquid reagent retaining portionof the microchip shown in FIG. 14 includes therein a partition 430dividing the liquid reagent retaining portion into two regions, namely afirst region A where a through opening forming the liquid reagent inletis provided and a second region B where the reagent outlet is provided.Partition 430 is constituted of a protrusion 431 provided on a firstsubstrate 500, a protrusion 432 provided on a second substrate 600 and acommunication gate 433 formed by a space between a flat surface at theleading end of protrusion 431 and a flat surface at the leading end ofprotrusion 432, for allowing communication between first region A andsecond region B. As described above, respective protrusions forming thepartition may be provided on both of the first substrate and the secondsubstrate respectively and the communication gate may be disposed in (ornear) the middle portion, instead of the ceiling or bottom of the liquidreagent retaining portion.

Like the liquid reagent retaining portion shown in FIGS. 11 and 12, theflat surface at the leading end of protrusion 431 and the flat surfaceat the leading end of protrusion 432 are preferably parallel orsubstantially parallel to each other. The angle formed by the surface offirst substrate 500 that forms first region A and the first-regionA-side side surface of protrusion 431 which is provided on the surfaceof first substrate 500 is preferably an obtuse angle, and morepreferably 95° or more. Likewise, the angle formed by the surface ofsecond substrate 600 that forms first region A and the first-regionA-side side surface of protrusion 432 which is provided on the surfaceof the second substrate 600 is preferably an obtuse angle, and morepreferably 95° or more.

Fourth Embodiment

A microchip of the present embodiment will be described in connectionwith a preferred example thereof. While characteristic features of themicrochip of the present embodiment will be chiefly described below,other features are similar to those of the first embodiment as describedabove.

FIG. 15 is a plan view showing a preferred example of a first substrate1500 having a groove formed in a surface and used for the microchip ofthe present embodiment. FIG. 15 shows the groove-formed surface of firstsubstrate 1500. The microchip of the present embodiment is formed bysuperposing and bonding first substrate 1500 on a second substrate (notshown) having an identical or similar outline form to first substrate1500, in such a manner that the groove-formed surface of first substrate1500 is located opposite to the second substrate. First substrate 1500and the second substrate are respectively a plastic transparentsubstrate and a plastic black substrate, for example.

Referring to FIG. 15, the microchip of the present embodiment is chieflyconstituted of a sample tube mount portion 1501 for incorporating asample tube such as capillary containing the whole blood taken from asubject, a blood plasma separating portion 1502 for removing componentssuch as blood cell from the whole blood drawn from the sample tube toobtain a blood plasma component, a sample measuring portion 1503 formeasuring the separated blood plasma component, two liquid reagentretaining portions 1, 2 serving as fluid retaining reservoirs forretaining a liquid reagent, two liquid reagent measuring portions 1506,1507 for measuring a liquid reagent, mixing portions 1508, 1509, 1510,and 1511 for mixing the blood plasma component with a liquid reagent,and a detecting portion 1512 where a test and an analysis are conductedfor the resultant liquid mixture. The two liquid reagent retainingportions 1, 2 respectively include liquid reagent inlets 3, 1513 forinjecting a liquid reagent therefrom. Liquid reagent inlets 3, 1513 areeach a through opening extending through first substrate 1500 in thethickness direction.

FIG. 16 is an enlarged plan view of liquid reagent retaining portion 1in first substrate 1500 shown in FIG. 15. As shown in FIG. 16, liquidreagent retaining portion 1 includes a fluid outlet 4 for allowing theliquid reagent contained in the retaining portion to flow out. The endof the opening of fluid outlet 4 is made very small to such an extentsufficient to cause capillary action. This shape of the openingeffectively suppresses unintended leakage of the liquid reagent fromliquid reagent retaining portion 1.

Liquid reagent retaining portion 1 includes therein one or more columnarbodies 5 extending in the thickness direction of the microchip. Columnarbody 5 is provided in a fluid retaining region where the farthestposition from fluid outlet 4 in liquid reagent retaining portion 1 isincluded and a fluid is retained. “Fluid retaining region” refers to aregion where a predetermined amount (may be the whole amount) of fluid(liquid reagent) introduced into a fluid containing reservoir (liquidreagent retaining portion) is located. The fluid is preferably retainedas a mass by a surface tension or the like.

FIG. 17 is an enlarged view showing an arrangement of columnar bodies 5in liquid reagent retaining portion 1 shown in FIG. 16. FIG. 18 is aplan view showing a relation between a plurality of columnar bodies 5 inliquid reagent retaining portion 1 shown in FIG. 16 and the liquidreagent retained in liquid reagent retaining portion 1.

As shown in FIG. 17, liquid reagent retaining portion 1 shown in FIG. 16includes three or more columnar bodies 5, and columnar bodies 5 arearranged in such a manner that each columnar body is located at a vertexposition of a substantially regular triangle. Namely, in FIG. 17,columnar bodies 5 are each disposed to form a regular triangle withother adjacent columnar bodies 5. Here, length L1 of one side of theregular triangle is preferably 0.1 to 1 mm, and particularly preferably0.5 to 1 mm. It is supposed here that “length of one side” refers to thedistance between respective centers of a plurality of columnar bodies 5as shown in FIG. 17. “Substantially regular triangle” is preferably atriangle having angles θ1 and θ2 in FIG. 17 of 60° each. However,“substantially regular triangle” here also includes a triangle whereangles θ1 and θ2 are each 45 to 75°.

As a plurality of columnar bodies 5 are arranged to form a substantiallyregular triangle, tensile forces are uniformly exerted by columnarbodies 5 on the retained liquid reagent 7, so that liquid reagent 7 canbe retained stably. Further, as a plurality of columnar bodies 5 arearranged to form a substantially regular triangle, the liquid reagentcan be efficiently retained without excessively increasing the areaoccupied by the fluid retaining region.

Length L1 may be appropriately set to an optimum length according to thewettability (angle of contact) of the liquid reagent contained in liquidreagent retaining portion 1. Basically, however, a fluid (liquidreagent) with any angle of contact can be retained in the fluidretaining region as long as length L1 is 0.1 to 1 mm. In the liquidreagent retaining portion shown in FIG. 16, columnar bodies 5 are eacharranged at a vertex position of a substantially regular triangle. Thecolumnar bodies, however, may not be arranged in this manner. In thiscase, the distance between columnar bodies 5 is preferably 0.1 to 1 mm.

As shown in FIG. 18, it is preferable that liquid reagent retainingportion 1 includes two or more columnar bodies 5, and columnar bodies 5are arranged on the liquid surface of liquid reagent 7 that is formedwhen the whole amount of liquid reagent 7 which is a fluid contained inliquid reagent retaining portion 1 is retained in the above-describedfluid retaining region.

Specifically, an arrangement of two more columnar bodies 5 and theliquid surface of liquid reagent 7 in the fluid retaining region aremade coincident with each other, so that the surface tension of liquidreagent 7 can be utilized to more efficiently retain liquid reagent 7 inthe fluid retaining region. In the case where a plurality of columnarbodies 5 are arranged on the liquid surface (fluid surface) of liquidreagent 7, liquid reagent 7 is caught in the state of protruding fromthe portion between a plurality of columnar bodies 5 by the surfacetension, and thus liquid reagent 7 is retained in the fluid retainingregion. Columnar bodies 5 arranged on the liquid surface of liquidreagent 7 may be arranged in the shape of an arc of a circle whosecenter is the start point C of fluid outlet 4.

In liquid reagent retaining portion 1 shown in FIG. 16, a partition 6 isprovided for dividing liquid reagent retaining portion 1 into twosections, namely a first region including liquid reagent inlet 3 and asecond region including fluid outlet 4 (see FIG. 16). A similarpartition is also provided in liquid reagent retaining portion 2.

Partition 6 has, at its two opposing ends, two communication gatesrespectively for allowing communication between the first region and thesecond region. When liquid reagent 7 is injected from liquid reagentinlet 3 into liquid reagent retaining portion 1 having partition 6,liquid reagent 7 contained in the first region is less likely to flowinto the second region, even if impact is exerted on the microchip,since the two communication gates function as a valve. The regionequally distant from the two communication gates maybe theabove-described fluid retaining region. As described below, themicrochip of the present embodiment includes columnar body 5 so thatliquid reagent retaining portion 1 can be appropriately made in adesired shape.

The liquid reagent retaining portion in the microchip of the presentembodiment has an excellent liquid reagent retaining capability againstimpact, so that unintended outflow of the liquid reagent from the liquidreagent retaining portion due to impact can be effectively suppressed orprevented. The valve function here means that undesired discharge of theliquid reagent is prevented, while desired discharge of the liquidreagent can be accomplished by application of a centrifugal force with apredetermined strength. In liquid reagent retaining portion 1 shown inFIG. 16, fluid outlet 4 also has the valve function. Therefore, liquidreagent retaining portion 1 is structured in such a manner that leakageof the liquid reagent to the outside is extremely unlikely to occurbecause of the synergetic effect provided by the three structures,namely columnar body 5, partition 6 and fluid outlet 4.

In liquid reagent retaining portion 1 shown in FIG. 16, it is preferablethat liquid reagent inlet 3 is disposed between fluid outlet 4 and thefluid retaining region, and that two or more columnar bodies 5 arearranged in the direction substantially perpendicular to a straight lineconnecting fluid outlet 4 and a center D of liquid reagent inlet 3. Itis also preferable that the outermost columnar bodies are locatedsubstantially perpendicular to a straight line connecting fluid outlet 4and a center D of liquid reagent inlet 3. Here, “substantiallyperpendicular” refers to the state where angle θ3 shown in FIG. 18 is ina range of 60 to 120°. With this arrangement, outflow of liquid reagent7 from fluid outlet 4 can be effectively suppressed.

The shape of columnar body 5 may be a circular cylinder as shown in FIG.17, a column having a polygonal cross section, or a body tapering towardat least one end (such as cone, pyramid, fusiform body). Columnar body 5may have a void or protrusion for example. In terms of easiness ofmolding, however, it is preferable to provide a columnar body of acircular cylinder in shape at the first substrate. Referring to FIG. 17,in the case where columnar body 5 is a circular cylinder, diameter L2 ispreferably 0.3 to 1.5 mm, and particularly preferably 0.5 to 1.0 mm.When diameter L2 of columnar body 5 is in this range, the ability toretain liquid reagent 7 is further improved since the density of thearrangement of columnar bodies 5 and the area of contact betweencolumnar bodies 5 and the fluid are appropriately set.

FIG. 19 is a cross sectional view along line XIX-XIX in FIG. 16. Asshown in FIG. 19, length L3 of columnar body 5 in the thicknessdirection of the microchip is preferably substantially identical todepth L4 of the groove forming liquid reagent retaining portion 1. Inthe case where L3 and L4 are substantially equal to each other,particularly the surface tension of liquid reagent 7 can be used to themaximum extent to retain liquid reagent 7 in the fluid retaining region.

The difference between length L3 of columnar body 5 in the thicknessdirection of the microchip and depth L4 of the groove is preferably 0 to0.5 mm and particularly preferably 0 to 0.1 mm. When the differenceexceeds 0.5 mm, there is a possibility that liquid reagent 7 could notbe retained in the fluid retaining region. In the case where a pluralityof columnar bodies 5 are arranged, respective lengths L3 are preferablyidentical to each other. These lengths L3, however, may be differentfrom each other.

While respective shapes (diameter L2, length L3) of columnar bodies 5are preferably identical to each other in liquid reagent retainingportion 1, columnar bodies 5 having different shapes may be present inthe same retaining portion.

Further, the liquid reagent retaining portion of the present embodimentmay include, in addition to columnar bodies extending in the thicknessdirection of the microchip, a structural body extending perpendicularlyto the thickness direction and connecting these columnar bodies. Namely,the columnar body of the present embodiment includes a mesh-likestructural body as long as a columnar body extending in the thicknessdirection of the microchip is included. In the case where the mesh-likecolumnar body is provided, the ability to retain the liquid reagent canbe further improved.

FIG. 20 is a plan view showing a microchip without columnar body,provided as a reference drawing relative to the microchip of the presentembodiment.

The microchip shown in FIG. 20 includes liquid reagent retainingportions 21, 22, and liquid reagent retaining portions 21, 22 eachinclude a fluid outlet 24, a liquid reagent inlet 23 and a partition 26.Liquid reagent retaining portions 21, 22 retain a liquid reagent 27.Since partition 26 is provided, movement of liquid reagent 27 towardfluid outlet 24 can be hindered to a certain degree.

In the microchip shown in FIG. 20 without columnar body, it is necessaryto increase the area of contact between the inner wall surface of liquidreagent retaining portions 21, 22 and liquid reagent 27 as much aspossible, in order to enhance the ability to retain the liquid reagent.In this case, the shape of liquid reagent retaining portions 21, 22could be restricted in consideration of the contact area with liquidreagent 27.

In contrast, since the microchip of the present embodiment includes thecolumnar body, the shape of the liquid reagent retaining portion can beselected from a broader variety of different shapes. Accordingly, theform of the entire fluid circuit of the microchip can include a broadervariety of different forms. As compared with the case where no columnarbody is provided, the liquid reagent can be more firmly retained in thefluid retaining region of the liquid reagent retaining portion.

Here, the columnar body may be formed at any one of the first substrateand the second substrate. For example, the columnar body may be formedin a region corresponding to the liquid reagent retaining portion of thesurface provided with the groove forming the fluid circuit of the firstsubstrate, or the columnar body may be formed at a surface of the secondsubstrate.

An operational method of the microchip shown in FIG. 15 will begenerally described. Here, the operational method described below is anexemplary one, and is not limited to the method as described. First, asample tube into which a sample of the whole blood is taken is insertedinto sample tube mount portion 1501. Next, a centrifugal force in theleftward direction with respect to FIG. 15 (hereinafter simply referredto as leftward centrifugal force, centrifugal forces in other directionswill be called similarly below) is applied to the microchip to draw outthe whole-blood sample in the sample tube. After this, a downwardcentrifugal force is applied to cause the whole-blood sample to beintroduced into blood plasma separating portion 1502 where the blood isseparated into a blood plasma component and a blood cell component bycentrifugal separation. When the whole blood sample is introduced intoblood plasma separating portion 1502, some of the whole-blood sampleoverflowing from blood plasma separating portion 1502 is received in awaste liquid storage 1515. The downward centrifugal force also causesthe liquid reagent retained in the fluid retaining region of liquidreagent retaining portion 2 to flow through the fluid outlet and to beintroduced into liquid reagent measuring portion 1506 where the liquidreagent is measured.

Then, a rightward centrifugal force is applied to introduce theseparated blood plasma component into sample measuring portion 1503. Atthis time, the measured liquid reagent is caused to move to mixingportion 1509, and the liquid reagent in liquid reagent retaining portion1 is discharged from the fluid outlet.

Next, a downward centrifugal force is applied to mix the measured bloodplasma component with the measured liquid reagent in mixing portion1508, while the liquid reagent discharged from liquid reagent retainingportion 1 is measured in liquid reagent measuring portion 1507. Then,rightward, downward and rightward centrifugal forces are successivelyapplied to cause the liquid mixture to flow between mixing portions 1508and 1509, so that the liquid mixture is sufficiently mixed. Next, anupward centrifugal force is applied to mix the liquid mixtureconstituted of the liquid reagent and the blood plasma component, withthe measured liquid reagent in mixing portion 1510. Then, leftward,upward, leftward and upward centrifugal forces are applied successivelyto move the liquid mixture between mixing portions 1510 and 1511 so thatthe liquid mixture is sufficiently mixed. Finally, a rightwardcentrifugal force is applied to introduce the liquid mixture in mixingportion 1510 into detecting portion 1512. Light is applied to detectingportion 1512 and optical measurement is performed on the liquid mixturein detecting portion 1512, such as measurement of the intensity of thetransmitted light, for example.

EXAMPLES

In the following, the present invention will be described in more detailin connection with examples. The present invention, however, is notlimited to these examples.

Example 1

A microchip was produced by bonding together a first substrate formed ofa transparent plastic substrate and having the structure shown in FIGS.1 and 2 and a second substrate that was a black substrate, by means oflaser welding. All of the communication gates had a width of 0.3 mm. Thebottom of the groove in the first substrate forming the upper inner wallof the communication gate was an inclined surface as shown in FIG. 4.Dimensions W4 and W5 shown in FIG. 4 were respectively 2.5 mm and 0.3mm. Into liquid reagent retaining portions 104 and 105 of thismicrochip, 20 μL of a buffer fluid and 20 μL of a latex reagent wereinjected respectively, and thereafter a sealing label was attached tothe surface of the microchip to seal liquid reagent inlets 113 and 114.Then, the microchip was wrapped with aluminum and further individuallypackaged in a paper box. Next, the packaged microchip was retained in arefrigerator for an hour at 8° C.

For the microchip immediately after taken out from the refrigerator, afree-fall impact test was conducted (five free falls from a height of 2m to a floor of rubber mat). As a result, in none of the liquid reagentretaining portions, the liquid reagent flowed out into second region B.

Next, the microchip having undergone the impact test was retained in anenvironment of 25° C. for ten minutes to increase the internal pressureof the liquid reagent retaining portion (internal-pressure elevationtest). As a result, although a slight amount of liquid reagent flowedout into second region B, most of the liquid reagent was retained infirst region A.

Comparative Example 1

Ten microchips were produced similarly to Example 1 except that a firstsubstrate without partition was used, and an impact test and an internalpressure elevation test were conducted. As a result of the impact test,it was found that, in all liquid reagent retaining portions of allmicrochips, the liquid reagent moved to close the inside opening of theoutflow channel. Further, as a result of the internal pressure elevationtest, in nine microchips out of the ten microchips, the liquid reagentin liquid reagent retaining portion 104 flowed out from the liquidreagent retaining portion. Similarly, in nine microchips out of the tenmicrochips, the liquid reagent in liquid reagent retaining portion 105flowed out from the liquid reagent retaining portion.

Comparative Example 2

Ten microchips were produced and an impact test was performed similarlyto Comparative Example 1 except that a pin hole was made in the sealinglabel on liquid reagent inlets 113 and 114 in order to prevent theinternal pressure of the liquid reagent retaining portion fromincreasing due to a temperature increase. As a result, deterioration ofthe valve function of the outflow channel caused the liquid reagent inliquid reagent retaining portion 104 to flow out from the liquid reagentretaining portion in six microchips out of the ten microchips. Further,in ten microchips out of the ten microchips, the liquid reagent inliquid reagent retaining portion 105 flowed out from the liquid reagentretaining portion.

Example 2

A microchip was produced by bonding together a first substrate formed ofa transparent plastic substrate having the structure shown in FIGS. 10,11 and 12 and a second substrate that was a black substrate, by means oflaser welding. Here, Height S of communication gate 1032 was 0.15 mm andlength Y of communication gate 1032 was 0.6 mm. The depth of the liquidreagent retaining portion (depth: distance between first substrate 1000and second substrate 200 in the liquid reagent retaining portion,corresponding to distance R in FIG. 12) was 2.8 mm. Curved portion 1033was arc-shaped and the radius of curvature of the arc was 3.45 mm. Theangle (angle α shown in FIG. 12) between the substrate surface formingfirst region A of first substrate 1000 and inclined surface F was 110°,and the angle (angle β in FIG. 12) between the substrate surface formingregion B of first substrate 1000 and the side surface of protrusion 1031on second region B side was 90°. Purified water was injected into liquidreagent retaining portion 1005 of the microchip, and thereafter asealing label was attached to the surface of the microchip to sealliquid reagent inlet 1017. Then, the following evaluation tests werecarried out.

(1) Evaluation of Fluid Operation

In the downward direction with respect to FIG. 10, a centrifugal force(3000 rpm, ten seconds) was applied, and thereafter a rightwardcentrifugal force (3000 rpm, ten seconds) was applied to introduce thepurified water in liquid reagent retaining portion 1005 into liquidreagent container 1007. At this time, no liquid was left in liquidreagent retaining portion 1005.

(2) Fall Test

The microchip was caused to fall from a height of 2 m 20 times. As aresult, the purified water did not flow out into second region B.

(3) Pressure Test

In an environment at a temperature of 4° C., the purified water inliquid reagent retaining portion 1005 was moved intentionally to contactpartition 1030, and thereafter the microchip was left in a 37° C.environment for 20 minutes. While the internal pressure of first regionA increased according to the temperature increase, the purified waterdid not flow out into second region B.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the scopeof the present invention being interpreted by the terms of the appendedclaims.

1-7. (canceled)
 8. A microchip comprising: a first substrate and asecond substrate, said first substrate being superposed on said secondsubstrate and having a surface with a groove; and a fluid circuitcomposed of a cavity defined by said groove and a surface on said firstsubstrate side of said second substrate, wherein said fluid circuitincludes a fluid retaining reservoir for retaining a fluid, said fluidretaining reservoir includes: a fluid outlet for allowing said fluid toflow out from said fluid retaining reservoir; and a partition dividingsaid fluid retaining reservoir into a first region where said fluid isintroduced and a second region where said fluid outlet is included, saidpartition includes a communication gate for allowing communicationbetween said first region and said second region, and at least a part ofsaid partition includes a curved portion formed of a wall in a shape ofa curve as seen from a surface of said microchip.
 9. The microchipaccording to claim 8, wherein said curved portion is formed of a wall ina shape of an arc protruding toward said second region.
 10. Themicrochip according to claim 9, wherein said arc has a radius ofcurvature of 2 to 5 mm.
 11. The microchip according to claim 8, whereina side surface of said partition abutting on said first region has aninclined surface inclined with respect to thickness direction of themicrochip.
 12. The microchip according to claim 8, wherein saidpartition is composed of a protrusion provided on a surface of saidfirst substrate or said second substrate, and said communication gate iscomposed of a space defined between said protrusion and an oppositesurface of said second substrate or said first substrate.
 13. Themicrochip according to claim 12, wherein a surface of said protrusionforming said communication gate extends parallel or substantiallyparallel to said opposite surface of the second substrate or the firstsubstrate.
 14. The microchip according to claim 12, wherein an anglebetween the surface of said first substrate or said second substratehaving said protrusion provided thereon and forming said first region,and a side surface of said protrusion abutting on said first region, isan obtuse angle.
 15. The microchip according to claim 8, wherein saidpartition is composed of respective protrusions provided on respectivesurfaces of said first substrate and said second substrate, and saidcommunication gate is composed of a space defined between the protrusionprovided on the surface of said first substrate and the protrusionprovided on the surface of said second substrate.
 16. The microchipaccording to claim 15, wherein the protrusion provided on the surface ofsaid first substrate and the protrusion provided on the surface of saidsecond substrate have respective surfaces forming said communicationgate that are parallel to or substantially parallel to each other. 17.The microchip according to claim 15, wherein an angle between thesurface of said first substrate forming said first region, and a sidesurface, abutting on said first region, of said protrusion provided onthe surface of said first substrate, is an obtuse angle, and an anglebetween the surface of said second substrate forming said first region,and a side surface, abutting on said first region, of said protrusionprovided on the surface of said second substrate, is an obtuse angle.18-25. (canceled)